# Retell AI

> Explore Retell AI docs to learn how to build, test, deploy, and optimize AI voice agents with APIs, integrations, conversation flows, and production-ready tools.

## Docs

- [Access Control](https://docs.retellai.com/accounts/access-control.md): Manage your Retell workspace with role-based access control: invite members, assign Admin, Developer, Analyst, or Viewer roles, and control permissions.
- [Manage your Retell AI account](https://docs.retellai.com/accounts/account.md): Check account status, reset your password, switch to Google SSO, stop charges, and delete your Retell AI account when no longer needed.
- [Add payment methods](https://docs.retellai.com/accounts/add-payment.md): Add a Stripe payment method to your Retell workspace to buy credits, keep calling after the free trial, purchase phone numbers, and avoid service interruptions.
- [API Key Overview](https://docs.retellai.com/accounts/api-keys-overview.md): How API keys authenticate your Retell REST API requests, SDK integrations, and webhook endpoints, plus best practices for storing and rotating keys safely.
- [Billing overview](https://docs.retellai.com/accounts/billing.md): How Retell billing works: prepaid credits and auto recharge on credit-based accounts, end-of-month billing on legacy accounts, plus usage tracking and invoices.
- [Exceptions to Our Per-Minute Pricing](https://docs.retellai.com/accounts/billing-exceptions.md): Billing adjustments that may affect Retell call costs: 10-second minimum for dynamic opening messages and extra charges for long prompt token counts.
- [Data Retention Policy](https://docs.retellai.com/accounts/data-retention.md): Configure per-agent data retention to automatically delete call and chat data — transcripts, recordings, and logs — after a set period for compliance.
- [Handle failed payments](https://docs.retellai.com/accounts/fail-payment.md): Resolve failed Retell payments: contact your bank to allowlist transactions, request written confirmation, and update your payment method on Stripe.
- [KYC Verification](https://docs.retellai.com/accounts/kyc.md): Complete KYC verification — automatic, Persona-based, or manual review — to unlock outbound calling, phone number purchases, and SMS on your Retell account.
- [Manage API keys and permission scopes](https://docs.retellai.com/accounts/manage-api-keys.md): Create, delete, and rotate Retell API keys, set a webhook signing key, and restrict permissions with read or edit scopes for Build, Monitor, and Deploy.
- [Data Storage Settings](https://docs.retellai.com/accounts/privacy-disable.md): Control how Retell stores sensitive call data — recordings, transcripts, dynamic variables, caller IDs, KB logs — with per-agent privacy settings.
- [Public Keys](https://docs.retellai.com/accounts/public-keys.md): How Retell public keys authenticate the Chat Widget from your frontend, what they can and cannot access, and how to safely embed them in client-side code.
- [Opt in to secure URL](https://docs.retellai.com/accounts/signed-secure-url.md): Opt in to secure URLs so Retell-generated call recording and log links automatically expire after 24 hours, preventing unauthorized access if a link leaks.
- [Create and manage Retell workspaces](https://docs.retellai.com/accounts/workspace.md): Create and manage Retell workspaces, find your workspace ID, invite teammates to collaborate, switch between workspaces, and safely delete a workspace.
- [Set language for your agent](https://docs.retellai.com/agent/language.md): Set a single language for a Retell agent to control speech recognition, voice pronunciation, and the language the agent uses to respond during calls.
- [Configure a multilingual agent](https://docs.retellai.com/agent/multilingual.md): Configure a Retell multilingual agent: pick which languages it supports, understand ASR and TTS accuracy trade-offs, and when single-language is a better fit.
- [Setup versioning and tags for agents](https://docs.retellai.com/agent/version.md): Use Retell agent versions and environment tags to lock in production configurations, track change history, and roll back drafts without breaking live calls.
- [Compare agent versions](https://docs.retellai.com/agent/version-comparison.md): Compare any two versions of a Retell agent side by side to review prompt, voice, tool, and flow changes before publishing or auditing past modifications.
- [Address metric issues](https://docs.retellai.com/ai-qa/address-metric-issues.md): Step-by-step fixes for common AI QA metric issues — hallucinations, knowledge base mistakes, overlapping speech, latency, sentiment, and tool errors.
- [Define a QA cohort](https://docs.retellai.com/ai-qa/create-cohort.md): Define a Retell AI QA cohort: pick agents, date range, and call filters, then set a sampling rate to control evaluation volume and cost.
- [Define resolution criteria](https://docs.retellai.com/ai-qa/define-resolution-criteria.md): Define resolution criteria for an AI QA cohort using AI-evaluated conditions and performance metric thresholds to decide whether each call counts as successful.
- [Access AI QA](https://docs.retellai.com/ai-qa/get-started.md): Get started with Retell AI QA: open the AI QA tab from the sidebar and click Create QA to launch your first automated call quality evaluation.
- [AI Quality Assurance](https://docs.retellai.com/ai-qa/overview.md): AI QA scores Retell calls on hallucination, knowledge base accuracy, latency, sentiment, and tool usage to surface quality trends and issues.
- [AI QA metrics](https://docs.retellai.com/ai-qa/terminologies.md): Reference for every AI QA metric and term — average latency, hallucination rate, KB accuracy, overlapping speech, sentiment — and how each one is evaluated.
- [View QA results](https://docs.retellai.com/ai-qa/view-qa-results.md): Read your Retell AI QA results: review aggregate metrics and trends, drill into individual calls, inspect transcripts with QA diagnostics, and calibrate scores.
- [Add Knowledge Base Sources](https://docs.retellai.com/api-references/add-knowledge-base-sources.md): Add sources to a knowledge base
- [Add Voice](https://docs.retellai.com/api-references/add-voice.md): Add a community voice to the voice library
- [Agent Playground Completion](https://docs.retellai.com/api-references/agent-playground-completion.md): Stateless playground completion. Send the full conversation history (same shape as chat completion messages) and receive only the newly generated messages. Nothing is persisted server-side — the caller manages conversation state.
- [Clone Voice](https://docs.retellai.com/api-references/clone-voice.md): Clone a voice from audio files
- [Create Voice Agent](https://docs.retellai.com/api-references/create-agent.md): Create a new agent
- [Create Draft Agent Version](https://docs.retellai.com/api-references/create-agent-version.md): Create a new draft agent version from a base version.
- [Create Batch Call](https://docs.retellai.com/api-references/create-batch-call.md): Create a batch call
- [Create Batch Test](https://docs.retellai.com/api-references/create-batch-test.md): Create a batch test to run multiple test cases
- [Create Chat](https://docs.retellai.com/api-references/create-chat.md): Create a chat session
- [Create Chat Agent](https://docs.retellai.com/api-references/create-chat-agent.md): Create a new chat agent
- [Create Draft Chat Agent Version](https://docs.retellai.com/api-references/create-chat-agent-version.md): Create a new draft agent version from a base version.
- [Create Chat Completion](https://docs.retellai.com/api-references/create-chat-completion.md): Create a chat completion message
- [Create Conversation Flow](https://docs.retellai.com/api-references/create-conversation-flow.md): Create a new Conversation Flow that can be attached to an agent. This is used to generate response output for the agent.
- [Create Conversation Flow Subflow](https://docs.retellai.com/api-references/create-conversation-flow-component.md): Create a new shared conversation flow component
- [Create Knowledge Base](https://docs.retellai.com/api-references/create-knowledge-base.md): Create a new knowledge base
- [Create Phone Call](https://docs.retellai.com/api-references/create-phone-call.md): Create a new outbound phone call
- [Create Phone Number](https://docs.retellai.com/api-references/create-phone-number.md): Buy a new phone number & Bind agents
- [Create Retell LLM](https://docs.retellai.com/api-references/create-retell-llm.md): Create a new Retell LLM Response Engine that can be attached to an agent. This is used to generate response output for the agent.
- [Create Outbound SMS](https://docs.retellai.com/api-references/create-sms-chat.md): Start an outbound SMS chat conversation with a phone number using the specified agent. The agent must be configured for chat mode. The initial SMS message will be automatically generated and sent based on the agent's configuration.
- [Create Test Case Definition](https://docs.retellai.com/api-references/create-test-case-definition.md): Create a new test case definition
- [Create Web Call](https://docs.retellai.com/api-references/create-web-call.md): Create a new web call
- [Delete Agent](https://docs.retellai.com/api-references/delete-agent.md): Delete an existing agent
- [Delete Agent Version](https://docs.retellai.com/api-references/delete-agent-version.md): Delete a specific agent version.
- [Delete Call](https://docs.retellai.com/api-references/delete-call.md): Delete a specific call and its associated data
- [Delete Chat](https://docs.retellai.com/api-references/delete-chat.md): Delete an existing chat
- [Delete Chat Agent](https://docs.retellai.com/api-references/delete-chat-agent.md): Delete an existing chat agent
- [Delete Chat Agent Version](https://docs.retellai.com/api-references/delete-chat-agent-version.md): Delete a specific agent version.
- [Delete Conversation Flow](https://docs.retellai.com/api-references/delete-conversation-flow.md): Delete a conversation flow and all its versions
- [Delete Conversation Flow Subflow](https://docs.retellai.com/api-references/delete-conversation-flow-component.md): Delete a shared conversation flow component. When deleting a shared component, creates local copies for all linked conversation flows.
- [Delete Knowledge Base](https://docs.retellai.com/api-references/delete-knowledge-base.md): Delete an existing knowledge base
- [Delete Knowledge Base Source](https://docs.retellai.com/api-references/delete-knowledge-base-source.md): Delete an existing source from knowledge base
- [Delete Phone Number](https://docs.retellai.com/api-references/delete-phone-number.md): Delete an existing phone number
- [Delete Retell LLM](https://docs.retellai.com/api-references/delete-retell-llm.md): Delete an existing Retell LLM Response Engine
- [Delete Test Case Definition](https://docs.retellai.com/api-references/delete-test-case-definition.md): Delete a test case definition
- [End Chat](https://docs.retellai.com/api-references/end-chat.md): End an ongoing chat
- [Get Voice Agent](https://docs.retellai.com/api-references/get-agent.md): Retrieve details of a specific agent
- [Get Agent Versions](https://docs.retellai.com/api-references/get-agent-versions.md): Get all versions of an agent
- [Get Batch Test](https://docs.retellai.com/api-references/get-batch-test.md): Get a batch test job by ID
- [Get Call](https://docs.retellai.com/api-references/get-call.md): Retrieve details of a specific call
- [Get Chat](https://docs.retellai.com/api-references/get-chat.md): Retrieve details of a specific chat
- [Get Chat Agent](https://docs.retellai.com/api-references/get-chat-agent.md): Retrieve details of a specific chat agent
- [Get Chat Agent Versions](https://docs.retellai.com/api-references/get-chat-agent-versions.md): Get all versions of a chat agent
- [Get Concurrency](https://docs.retellai.com/api-references/get-concurrency.md): Get the current concurrency and concurrency limit of the org
- [Get Conversation Flow](https://docs.retellai.com/api-references/get-conversation-flow.md): Retrieve details of a specific Conversation Flow
- [Get Conversation Flow Subflow](https://docs.retellai.com/api-references/get-conversation-flow-component.md): Get a shared conversation flow component
- [Get Knowledge Base](https://docs.retellai.com/api-references/get-knowledge-base.md): Retrieve details of a specific knowledge base
- [Get MCP Tools](https://docs.retellai.com/api-references/get-mcp-tools.md): Get MCP tools for a specific agent
- [Get Phone Number](https://docs.retellai.com/api-references/get-phone-number.md): Retrieve details of a specific phone number
- [Get Retell LLM](https://docs.retellai.com/api-references/get-retell-llm.md): Retrieve details of a specific Retell LLM Response Engine
- [Get Test Case Definition](https://docs.retellai.com/api-references/get-test-case-definition.md): Get a test case definition by ID
- [Get Test Run](https://docs.retellai.com/api-references/get-test-run.md): Get a test case job (test run) by ID
- [Get Voice](https://docs.retellai.com/api-references/get-voice.md): Retrieve details of a specific voice
- [Import Phone Number](https://docs.retellai.com/api-references/import-phone-number.md): Import a phone number from custom telephony & Bind agents
- [List Voice Agents](https://docs.retellai.com/api-references/list-agents.md): List unique agents with pagination.
- [List Batch Tests](https://docs.retellai.com/api-references/list-batch-tests.md): List batch test jobs with pagination
- [List Calls](https://docs.retellai.com/api-references/list-calls.md): List calls with unified cursor pagination response.
- [List Chat Agents](https://docs.retellai.com/api-references/list-chat-agents.md): List unique agents with pagination.
- [List Chats](https://docs.retellai.com/api-references/list-chats.md): List chats with unified cursor pagination response.
- [List Conversation Flow Subflows](https://docs.retellai.com/api-references/list-conversation-flow-components.md): List shared conversation flow components with pagination
- [List Conversation Flows](https://docs.retellai.com/api-references/list-conversation-flows.md): List conversation flows with pagination
- [List Export Requests](https://docs.retellai.com/api-references/list-export-requests.md): List export requests with pagination
- [List Knowledge Bases](https://docs.retellai.com/api-references/list-knowledge-bases.md): List all knowledge bases
- [List Phone Numbers](https://docs.retellai.com/api-references/list-phone-numbers.md): List phone numbers with pagination
- [List Retell LLMs](https://docs.retellai.com/api-references/list-retell-llms.md): List Retell LLM Response Engines with pagination
- [List Test Case Definitions](https://docs.retellai.com/api-references/list-test-case-definitions.md): List test case definitions with pagination
- [List Test Runs](https://docs.retellai.com/api-references/list-test-runs.md): List test case jobs (test runs) for a batch test job with pagination
- [List Voices](https://docs.retellai.com/api-references/list-voices.md): List all voices available to the user
- [LLM WebSocket](https://docs.retellai.com/api-references/llm-websocket.md): LLM WebSocket protocol for streaming requests from Retell to your custom LLM server and returning responses, tool calls, and DTMF actions during a live call.
- [Retell AI API Reference](https://docs.retellai.com/api-references/overview.md): Reference for the Retell AI API: authentication, base URL, SDKs, and endpoints for building and managing voice and chat agents programmatically.
- [Publish Agent](https://docs.retellai.com/api-references/publish-agent.md): Publish an existing draft version in place.
- [Publish Chat Agent](https://docs.retellai.com/api-references/publish-chat-agent.md): Publish an existing draft version in place.
- [Register Phone Call](https://docs.retellai.com/api-references/register-phone-call.md): Register a new phone call for custom telephony
- [Rerun Call Analysis](https://docs.retellai.com/api-references/rerun-call-analysis.md): Rerun post-call analysis for a specific call. This operation incurs charges.
- [Rerun Chat Analysis](https://docs.retellai.com/api-references/rerun-chat-analysis.md): Rerun post-chat analysis for a specific chat. This operation incurs charges.
- [Search Voice](https://docs.retellai.com/api-references/search-voice.md): Search for community voices from voice providers
- [Stop Call](https://docs.retellai.com/api-references/stop-call.md): Stop an ongoing call.
- [Update Voice Agent](https://docs.retellai.com/api-references/update-agent.md): Update an existing agent's latest draft version
- [Update Call](https://docs.retellai.com/api-references/update-call.md): Update metadata and sensitive data storage settings for an existing call.
- [Update Chat](https://docs.retellai.com/api-references/update-chat.md): Update metadata and sensitive data storage settings for an existing chat.
- [Update Chat Agent](https://docs.retellai.com/api-references/update-chat-agent.md): Update an existing chat agent
- [Update Conversation Flow](https://docs.retellai.com/api-references/update-conversation-flow.md): Update an existing conversation flow
- [Update Conversation Flow Subflow](https://docs.retellai.com/api-references/update-conversation-flow-component.md): Update an existing shared conversation flow component
- [Update Live Call](https://docs.retellai.com/api-references/update-live-call.md): Update an ongoing call at runtime. Supports overriding dynamic variables, metadata, and the data storage setting on the running call, and controlling the live agent (inject context, trigger a response). These overrides take effect immediately on the live call; metadata and data storage setting chang…
- [Update Phone Number](https://docs.retellai.com/api-references/update-phone-number.md): Update agent bound to a purchased phone number
- [Update Retell LLM](https://docs.retellai.com/api-references/update-retell-llm.md): Update an existing Retell LLM Response Engine
- [Update Test Case Definition](https://docs.retellai.com/api-references/update-test-case-definition.md): Update a test case definition
- [Add pause or read slowly](https://docs.retellai.com/build/add-pause.md): Control speech pacing in Retell agents by adding spaced dashes for short pauses and longer Read Slowly markup for phone numbers, addresses, and confirmations.
- [Add custom pronunciation](https://docs.retellai.com/build/add-pronunciation.md): Control how Retell AI agents pronounce words with IPA, CMU, Mandarin Pinyin, or Cantonese Jyutping based on the selected voice provider and model.
- [Agent Handbook](https://docs.retellai.com/build/agent-handbook.md): Turn on Retell Agent Handbook presets to add best-practice prompts for personality, accuracy, and safety with one toggle — no manual prompt writing required.
- [Speech recognition providers](https://docs.retellai.com/build/asr-providers.md): An overview of Retell's speech recognition providers — Azure, Deepgram, and Soniox — and how Retell auto-routes based on your agent's configured languages.
- [Book Calendar](https://docs.retellai.com/build/book-calendar.md): Connect Cal.com to a Retell voice agent so callers can book appointments mid-conversation — set up event types, API keys, and the booking tool step by step.
- [Check Calendar Availability](https://docs.retellai.com/build/check-availability.md): Connect Cal.com to a Retell voice agent to fetch open time slots during a call so the agent can quote real availability before booking an appointment.
- [Call transfer node in conversation flow](https://docs.retellai.com/build/conversation-flow/call-transfer-node.md): Use a call transfer node to hand a Retell phone call off to a different number — supports Retell and imported numbers, with optional pre-transfer messages.
- [Code node](https://docs.retellai.com/build/conversation-flow/code-node.md): Run JavaScript in a Retell conversation flow with a Code node. Read dynamic variables and call metadata, make HTTP requests, and store results for later nodes.
- [Reusable subflows for conversation flow agents](https://docs.retellai.com/build/conversation-flow/components.md): Package parts of a conversation flow into reusable Retell subflows, so you can build complex agents once and share consistent logic across many flows.
- [Conversation node](https://docs.retellai.com/build/conversation-flow/conversation-node.md): Use Retell conversation nodes for multi-turn dialogue without tool calls — the default building block for capturing info and guiding callers through a flow.
- [Custom function in conversation flow](https://docs.retellai.com/build/conversation-flow/custom-function.md): Add a custom function to a Retell conversation flow to call your external API mid-call. Configure method, URL, headers, parameters, and responses.
- [Debug guide](https://docs.retellai.com/build/conversation-flow/debug-guide.md): Diagnose and fix Retell conversation flow agent issues — wrong responses, missed transitions, and prompt problems — with a step-by-step guide.
- [End node](https://docs.retellai.com/build/conversation-flow/end-node.md): Use an end node in a Retell conversation flow to terminate the call cleanly, optionally with a closing message generated from a prompt or static text.
- [Extract Dynamic Variable Node](https://docs.retellai.com/build/conversation-flow/extract-dv-node.md): Add an extract dynamic variable node to a Retell conversation flow to pull values from the dialogue and store them as text, number, boolean, or enum variables.
- [Finetune Examples](https://docs.retellai.com/build/conversation-flow/finetune-examples.md): Add finetune examples to Retell conversation, subagent, and function nodes to correct unexpected responses or transitions with concrete transcript snippets.
- [Flex Mode: dynamic conversation flow execution](https://docs.retellai.com/build/conversation-flow/flex-mode.md): Flex Mode compiles a Retell conversation flow into a single structured prompt at runtime so the agent can handle varied user behavior while keeping flow logic.
- [Function Node Overview](https://docs.retellai.com/build/conversation-flow/function-node.md): Call any prebuilt or custom function from a Retell conversation flow function node — the agent fires the function on entry and transitions on the result.
- [Global Node](https://docs.retellai.com/build/conversation-flow/global-node.md): Global nodes in a Retell conversation flow can be reached from anywhere in the agent — ideal for handling universal intents like callbacks and human handoff.
- [Configure global settings](https://docs.retellai.com/build/conversation-flow/global-setting.md): Configure global settings for a Retell conversation flow agent — voice, language, LLM, denoising, and other agent-level options on the empty canvas.
- [Logic Split Node](https://docs.retellai.com/build/conversation-flow/logic-split-node.md): Use a logic split node to branch a Retell conversation flow on rules — the agent evaluates conditions on entry and routes silently to the next node.
- [MCP node in conversation flow](https://docs.retellai.com/build/conversation-flow/mcp-node.md): Add an MCP node to a Retell conversation flow to call remote MCP server tools during a live call, with custom headers and authentication.
- [Nodes and edges](https://docs.retellai.com/build/conversation-flow/node.md): Nodes are the building blocks of Retell conversation flows. Learn every node type, how edges connect them, and how transition conditions advance calls.
- [Conversation flow agents: structured voice AI call control](https://docs.retellai.com/build/conversation-flow/overview.md): Build structured Retell voice agents with conversation flow — nodes for dialogue, tools, transfers, code, and transitions for precise call control.
- [Press Digit Node](https://docs.retellai.com/build/conversation-flow/press-digit-node.md): Press digit nodes let Retell agents navigate IVR menus by inferring and pressing the correct keypad digit silently during an outbound phone call.
- [SMS Node](https://docs.retellai.com/build/conversation-flow/sms-node.md): Use an SMS node to have a Retell voice agent send a text mid-call — to the caller or a different number — using an SMS-approved Retell or imported number.
- [Subagent node](https://docs.retellai.com/build/conversation-flow/subagent-node.md): Subagent nodes let a Retell conversation flow combine dialogue with on-the-fly tool calls — the LLM decides whether and when to use each attached tool.
- [Agent Transfer Node](https://docs.retellai.com/build/conversation-flow/transfer-agent-node.md): Agent transfer nodes (agent swap) hand a Retell call from one AI agent to another, useful for specialized agents, language switches, and modular call flows.
- [Transition conditions](https://docs.retellai.com/build/conversation-flow/transition-condition.md): Control when a Retell conversation flow agent moves between nodes: prompt conditions evaluated by the LLM, deterministic equation conditions, and else edges.
- [Conversational Mode](https://docs.retellai.com/build/conversational-mode.md): See how Conversational Mode rephrases your voice agent's replies — shorter, more natural, and more human than a typical assistant.
- [Create chat agent](https://docs.retellai.com/build/create-chat-agent.md): Build a Retell chat agent in the dashboard or API for text conversations, convert a voice agent to chat, and deploy via web widget, SMS, or API.
- [Dynamic variables: personalize Retell agent calls](https://docs.retellai.com/build/dynamic-variables.md): Inject per-call data into Retell agents using `{{variable_name}}` syntax for personalized greetings, context-aware responses, and dynamic call routing.
- [Expressive Mode: add emotion and emphasis to agent speech](https://docs.retellai.com/build/expressive-mode.md): Turn on Expressive Mode so Retell voice agents add emotion tags, sighs, pauses, and stressed words automatically or with manual overrides in your prompt.
- [Guardrails](https://docs.retellai.com/build/guardrails.md): Use Retell guardrails to detect prohibited topics in agent responses and user input, replacing flagged content with a safe placeholder so calls continue.
- [Handle background speech & noise](https://docs.retellai.com/build/handle-background-noise.md): Tune Retell denoising modes, interruption sensitivity, and background noise handling so your voice agent stays accurate in loud or noisy environments.
- [Handle voicemail and IVR](https://docs.retellai.com/build/handle-voicemail.md): Configure Retell agents to detect voicemails and IVR systems on outbound calls and choose what to do next — hang up, leave a message, or navigate the menu.
- [Knowledge base setup and retrieval tuning](https://docs.retellai.com/build/knowledge-base.md): Attach URLs, documents, and custom text to a Retell agent, then tune retrieval with query-rewrite instructions so it answers calls with accurate context.
- [Supported languages by provider](https://docs.retellai.com/build/language-support.md): Which Retell text-to-speech and speech recognition providers support each language, with the codes accepted by the API and model-level restrictions.
- [Configure LLM Options](https://docs.retellai.com/build/llm-options.md): Tune Retell LLM settings — temperature, fast tier, structured output, retries, timeouts — to balance reliability, latency, and cost for your voice agent.
- [Make agent hold and respond nothing](https://docs.retellai.com/build/no-response.md): Make a Retell agent stay silent on demand using the `NO_RESPONSE_NEEDED` stop sequence so it can hold for the caller without speaking or interrupting.
- [Build a Retell agent: configuration overview](https://docs.retellai.com/build/overview.md): Start building a Retell agent: pick an agent type, then configure the rest, including speech recognition, LLM responses, voice, and telephony behavior.
- [Platform voices](https://docs.retellai.com/build/platform-voices.md): Retell platform voices are a curated library tuned for phone conversations — clear at telecom bitrates, with automatic TTS fallback and no extra setup.
- [Prompt Engineering Guide](https://docs.retellai.com/build/prompt-engineering-guide.md): Best practices for writing Retell agent prompts that produce reliable, natural-sounding phone conversations — structure, examples, edge cases, and pitfalls.
- [Prompt guide & examples for specific situations](https://docs.retellai.com/build/prompt-situation-guide.md): Prompt examples for common voice agent situations — phone numbers, emails, dates, spellings, confirmations — many also available as Agent Handbook presets.
- [Code tool](https://docs.retellai.com/build/single-multi-prompt/code-tool.md): Run JavaScript as a tool in a Retell single- or multi-prompt agent. Read dynamic variables and metadata, make HTTP requests, and store structured results.
- [Step 2: Configure basic agent settings](https://docs.retellai.com/build/single-multi-prompt/configure-basic-settings.md): Set up a Retell single or multi-prompt agent: choose the language model, pick a voice and speaking speed, and decide who speaks first on the call.
- [Integrate any system with custom function](https://docs.retellai.com/build/single-multi-prompt/custom-function.md): Add a custom function to a Retell single- or multi-prompt agent to call your API mid-call. Configure URL, method, headers, parameters, and responses.
- [End call](https://docs.retellai.com/build/single-multi-prompt/end-call.md): Add the End Call tool to a Retell single or multi-prompt agent and define when the agent should automatically hang up based on conversation conditions.
- [Extract Dynamic Variables](https://docs.retellai.com/build/single-multi-prompt/extract-dv.md): Add the Extract Dynamic Variable tool to a Retell single- or multi-prompt agent to capture values from a call as typed dynamic variables.
- [Function Calling Overview](https://docs.retellai.com/build/single-multi-prompt/function-calling.md): Function calling lets Retell single or multi-prompt agents take real actions — transfer calls, end calls, book appointments, send SMS, and call external APIs.
- [MCP tools for single and multi-prompt agents](https://docs.retellai.com/build/single-multi-prompt/mcp.md): Connect a Retell single- or multi-prompt agent to a remote MCP server so it can call the server's tools during a live voice or chat conversation.
- [Press digit (IVR navigation)](https://docs.retellai.com/build/single-multi-prompt/press-digit.md): Enable Retell single or multi-prompt agents to navigate DTMF-input IVR menus by pressing keypad digits during outbound calls to reach the right department.
- [Single/Multi Prompt Agent Overview](https://docs.retellai.com/build/single-multi-prompt/prompt-overview.md): Choose between Retell single-prompt and multi-prompt agents based on call complexity — simple single prompt or staged prompts for state-driven conversations.
- [Send SMS](https://docs.retellai.com/build/single-multi-prompt/send-sms.md): Use the Send SMS tool so a Retell single or multi-prompt agent can text the caller or another number mid-call from SMS-enabled Retell or imported numbers.
- [Agent Transfer tool: hand a call to another AI agent](https://docs.retellai.com/build/single-multi-prompt/transfer-agent.md): Add the Agent Transfer (agent swap) tool to a Retell single or multi-prompt agent so it can hand the live call to another AI agent mid-conversation.
- [Transfer call tool (single & multi-prompt agents)](https://docs.retellai.com/build/single-multi-prompt/transfer-call.md): Add the Transfer Call tool to a Retell single or multi-prompt agent to route calls to a human, with cold, warm, and agentic warm transfer modes.
- [Build a multi-prompt agent](https://docs.retellai.com/build/single-multi-prompt/write-multi-prompt.md): Build a Retell multi-prompt agent by breaking the conversation into prompted states with explicit transitions between them — like a lead qualification flow.
- [Write a single prompt](https://docs.retellai.com/build/single-multi-prompt/write-single-prompt.md): Write a Retell single prompt agent using sectional prompts and clear instructions so the agent reliably follows your script across the full phone conversation.
- [Apply for branded call](https://docs.retellai.com/build/telephony/branded-call.md): Apply for Retell branded calling on US numbers so callers see your business name instead of a phone number — boost answer rates and reduce "Spam Likely".
- [Handle application rejection](https://docs.retellai.com/build/telephony/branded-call-rejection.md): Resolve rejected business profile, verified phone, and branded call applications on Retell — check rejection reasons in the dashboard and resubmit.
- [Add a business profile](https://docs.retellai.com/build/telephony/business-profile.md): Set up and verify a Retell business profile before applying for verified phone numbers or branded calling, with required company information and documents.
- [Spam likely overview](https://docs.retellai.com/build/telephony/call_efficiency_overview.md): Why phone numbers get marked "Spam Likely" by carriers and how Retell verified phone numbers and branded call services raise pickup rates on outbound calls.
- [Stop caller ID service](https://docs.retellai.com/build/telephony/delete-service.md): Stop active Retell caller-ID services — branded calls and verified phone numbers — without interrupting your underlying telephony or live agent calls.
- [Set & parse custom SIP headers](https://docs.retellai.com/build/telephony/sip-headers.md): Parse inbound and set outbound custom SIP headers in Retell to pass metadata between systems — supported for inbound, outbound, and transfer scenarios.
- [Apply for verified phone number](https://docs.retellai.com/build/telephony/verified-phone.md): Apply for a Retell verified phone number on US numbers to remove "Spam Likely" labels, increase trust with carriers, and improve outbound call pickup rates.
- [Balance between transcription accuracy and latency](https://docs.retellai.com/build/transcription-mode.md): Pick the right Retell transcription mode to balance accuracy against latency — interim results for speed or context-aware results for higher accuracy.
- [Setup TTS fallback](https://docs.retellai.com/build/tts-fallback.md): Configure TTS fallback voices so Retell agents keep speaking during a TTS provider outage — required when using custom or third-party provider voices.
- [TTS provider comparison](https://docs.retellai.com/build/tts-provider-comparison.md): Compare Retell TTS providers — ElevenLabs, Cartesia, and MiniMax — on spelling accuracy, voice naturalness, pacing, and accent support.
- [Capture DTMF input from user](https://docs.retellai.com/build/user-dtmf.md): Capture DTMF keypad input from callers in Retell agents — accept PINs, menu choices, and numeric entries, and configure completion timing and digit counts.
- [Choose a custom voice](https://docs.retellai.com/build/voice.md): Add custom voices to your Retell agent — search ElevenLabs community voices, import a voice clone, or train a clone for a unique brand-specific sound.
- [Give Conductor context](https://docs.retellai.com/conductor/add-context.md): Attach conversation steps, past calls, test cases, and files to your Conductor messages so its suggestions are accurate and tailored to your Retell agent.
- [Build & refine your agent](https://docs.retellai.com/conductor/build-and-refine.md): Chat with Conductor in plain English to build and improve your Retell agent — send your first message, use starter suggestions, write clear prompts.
- [Create an agent with Conductor](https://docs.retellai.com/conductor/create-agent.md): Generate a new Retell agent with Conductor by describing your use case in plain English and attaching reference files — get a working first version.
- [Conductor on the home page](https://docs.retellai.com/conductor/home.md): Access Conductor from the Retell home page to ask questions, plan changes, and work across multiple agents — without opening a specific agent first.
- [Manage your conversations](https://docs.retellai.com/conductor/manage-conversations.md): Start new chats, revisit past conversations, share a chat link, and give feedback in Conductor — so you can stay organized and help Conductor improve.
- [Meet Conductor](https://docs.retellai.com/conductor/overview.md): Conductor is the built-in AI assistant that helps you build, refine, and test your Retell agent in plain English — proposing changes for you to approve.
- [Review & apply changes](https://docs.retellai.com/conductor/review-changes.md): Review each change Conductor proposes to your Retell agent and accept or reject it. Nothing is applied until you approve — you stay fully in control.
- [Test & improve with Conductor](https://docs.retellai.com/conductor/test-and-improve.md): Use Conductor to review real calls, run simulations, and handle edge cases — so you can find problems and improve your Retell agent with confidence.
- [Free messages & pay-as-you-go](https://docs.retellai.com/conductor/usage-and-billing.md): Understand your daily free Conductor messages, turn on pay-as-you-go to keep working after they run out, and set a monthly spending limit for your workspace.
- [A/B Testing](https://docs.retellai.com/deploy/ab-testing.md): Run Retell A/B tests by splitting inbound and outbound voice and chat traffic between agents to compare prompts, voices, and flows in production.
- [Amazon Connect](https://docs.retellai.com/deploy/amazon-connect.md): Amazon Connect is a cloud-based contact center service from AWS that lets you set up and manage customer support call centers quickly.
- [Avaya](https://docs.retellai.com/deploy/avaya.md): A step-by-step guide to integrate Avaya Aura with Retell's SIP endpoints using Avaya SBCE as the border element to send and receive phone calls.
- [Retell Website Widget](https://docs.retellai.com/deploy/chat-widget.md): Embed the Retell website widget on your site with a single script tag — supports chat, voice, and callback modes powered by your chat and voice agents.
- [Understand concurrency & limits](https://docs.retellai.com/deploy/concurrency.md): Understand Retell concurrency and rate limits: max simultaneous calls, calls per second, burst mode, and per-workspace quota increases.
- [Implement chat with create chat completion](https://docs.retellai.com/deploy/create-chat-completion.md): Step-by-step guide to implementing chat functionality with a Retell chat agent using the create chat completion API for web and SMS channels.
- [Connect Retell voice agents to custom telephony](https://docs.retellai.com/deploy/custom-telephony.md): Integrate Retell voice agents with your own telephony provider using elastic SIP trunking or imported numbers from Twilio, Telnyx, and Vonage.
- [Send & receive SMS](https://docs.retellai.com/deploy/enable-sms.md): Enable SMS on Retell with Twilio numbers to send messages during calls, receive texts and MMS mid-call, and run two-way text conversations with chat agents.
- [Connect Five9 to Retell](https://docs.retellai.com/deploy/five9.md): Connect Five9 to Retell AI over the pre-built SIP trunk: import your Five9 number, add a ThirdPartyTransfer node, and route IVR calls to a voice agent.
- [Connect Genesys Cloud to Retell](https://docs.retellai.com/deploy/genesys.md): Set up a Genesys Cloud SIP phone trunk, number plans, and outbound routes to send inbound and outbound calls between Genesys and Retell agents.
- [Receive calls](https://docs.retellai.com/deploy/inbound-call.md): Bind voice agents to Retell or imported numbers to answer inbound calls, route SIP traffic, handle overflow, and pass per-call context.
- [International calling](https://docs.retellai.com/deploy/international-call.md): International calling rates and supported countries for Retell-managed numbers, plus how to enable outbound calls to global destinations from your workspace.
- [Create and schedule batch calls](https://docs.retellai.com/deploy/make-batch-call.md): Create, schedule, and monitor Retell batch calls in bulk to run outbound campaigns, send updates, or contact large recipient lists from a single workflow.
- [Make outbound calls](https://docs.retellai.com/deploy/outbound-call.md): Make outbound phone calls with Retell agents — bind agents to your numbers, prepare API credentials, and trigger calls programmatically or from the dashboard.
- [Purchase phone number](https://docs.retellai.com/deploy/purchase-number.md): Purchase Retell-managed US or Canada phone numbers directly in the dashboard — no telephony provider account required, ready for inbound and outbound calling.
- [Telnyx](https://docs.retellai.com/deploy/telnyx.md): Connect Retell to a Telnyx account with elastic SIP trunking — create the trunk, configure FQDN routing, set up outbound auth, and import Telnyx numbers.
- [Twilio](https://docs.retellai.com/deploy/twilio.md): Connect Retell to your Twilio account using elastic SIP trunking — set up termination, origination, credentials, and import Twilio numbers into Retell.
- [Vonage](https://docs.retellai.com/deploy/vonage.md): Connect Retell to a Vonage account using SIP trunking — configure termination and origination, set up credentials, and import Vonage numbers for calling.
- [Make a web call](https://docs.retellai.com/deploy/web-call.md): Add browser voice calls with the Retell Web SDK: create a web call server-side to get an access token, then start and control it from your frontend.
- [Explicit cold transfer mode selection (01/23/2026)](https://docs.retellai.com/deprecation-notice/2026/01-23_cold_transfer_mode_selection.md): On 01/23/2026 the `show_transferee_as_caller` field changes meaning — Retell switches to explicit cold transfer mode between SIP REFER and SIP INVITE.
- [Phone number single-agent fields removed (03/31/2026)](https://docs.retellai.com/deprecation-notice/2026/03-31_phone_number_agent_fields.md): On 03/31/2026 Retell deprecates single-agent fields on phone numbers in favor of weighted inbound, outbound, and SMS agent lists across the phone number APIs.
- [OpenAI Realtime and Cartesia Sonic replaced (04/03/2026)](https://docs.retellai.com/deprecation-notice/2026/04-03_model_replacements.md): On 04/03/2026 Retell replaces OpenAI Realtime models (gpt-4o-realtime, gpt-4o-mini-realtime) and Cartesia Sonic-2 and Sonic-Turbo with their newer counterparts.
- [Conversation node tools replaced by subagent (04/18/2026)](https://docs.retellai.com/deprecation-notice/2026/04-18_conversation_node_tools.md): On 04/18/2026 Retell deprecates `tools` and `tool_ids` on conversation nodes in favor of the new subagent node for dialogue that calls tools mid-call.
- [Claude Sonnet and Gemini Flash model upgrades (05/25/2026)](https://docs.retellai.com/deprecation-notice/2026/05-25_model_replacements.md): On 05/25/2026 Retell replaces Claude 4.0 Sonnet with 4.6 Sonnet and migrates Gemini 2.0 Flash, Flash-Lite, and 2.5 Flash to the newer Gemini 3.0 and 3.1 models.
- [Legacy list endpoints removed for v2/v3 (06/15/2026)](https://docs.retellai.com/deprecation-notice/2026/06-15_legacy_list_endpoints.md): On 06/15/2026 Retell removes legacy list endpoints (batch tests, conversation flows, phone numbers, Retell LLMs) — migrate to versioned v2 and v3 endpoints.
- [ElevenLabs Turbo models replaced with Flash (07/12/2026)](https://docs.retellai.com/deprecation-notice/2026/07-12_elevenlabs_turbo_models.md): On 07/12/2026, Retell replaces the ElevenLabs Turbo voice models (eleven_turbo_v2 and eleven_turbo_v2_5) with the Flash equivalents at lower latency.
- [Unified publish-agent-version endpoint (07/20/2026)](https://docs.retellai.com/deprecation-notice/2026/07-20_agent_version_endpoints.md): On 07/20/2026 Retell deprecates the legacy publish-agent and publish-chat-agent endpoints — migrate to the unified publish-agent-version endpoint.
- [Legacy MCP server (retell.stlmcp.com) removed (07/20/2026)](https://docs.retellai.com/deprecation-notice/2026/07-20_legacy_mcp_server.md): The legacy hosted MCP server at retell.stlmcp.com shuts down on 07/20/2026. Migrate your MCP client to mcp.retellai.com — auth is unchanged.
- [Legacy agent list endpoints removed (07/31/2026)](https://docs.retellai.com/deprecation-notice/2026/07-31_agent_list_endpoints.md): On 07/31/2026 Retell removes GET /list-agents and GET /list-chat-agents. Migrate to the unified POST /v2/list-agents endpoint with filters.
- [Multilingual agent locale array required (07/31/2026)](https://docs.retellai.com/deprecation-notice/2026/07-31_legacy_multilingual_setting.md): On 07/31/2026, the scalar "multi" value of the agent language field is removed in favor of an explicit locale array for multilingual Retell agents.
- [Update Call restricted to ended calls (08/31/2026)](https://docs.retellai.com/deprecation-notice/2026/08-31_update_call_ended_calls_only.md): Update Call becomes ended-calls-only on 08/31/2026; override_dynamic_variables and mid-call data_storage_setting changes move to Update Live Call.
- [Deprecation Overview](https://docs.retellai.com/deprecation-notice/overview.md): Browse upcoming and past Retell API deprecations and breaking changes by date — subscribe via RSS to get notified when new deprecation notices are posted.
- [Alert rules for call and chat metrics](https://docs.retellai.com/features/alerting-overview.md): Create Retell AI alert rules that email or webhook you when call or chat volume, success rate, cost, latency, or API errors cross a threshold you set.
- [Analytics dashboard](https://docs.retellai.com/features/analytics-dashboard.md): Build custom Retell analytics dashboards to track call and chat metrics like success rate, latency, cost, and concurrency, with charts, filters, and breakdowns.
- [Contacts](https://docs.retellai.com/features/contacts.md): Manage the people your Retell agents call and text: contact records keyed by phone number, custom contact fields, post-call data mappings, and CRM sync.
- [Inbound call & SMS webhook](https://docs.retellai.com/features/inbound-call-webhook.md): Use the Retell inbound webhook to dynamically pick the agent, set dynamic variables, reject calls, and pass per-call context for inbound phone and SMS.
- [Monitor live calls](https://docs.retellai.com/features/live-monitoring.md): Watch ongoing Retell calls in real time from the dashboard: follow the live transcript, listen in silently, take over from the agent, or end a call.
- [Consume the analysis data](https://docs.retellai.com/features/post-call-analysis-consumption.md): Consume Retell post-call analysis results through the dashboard, webhooks, or API — extract structured fields and feed them into your CRM and reporting tools.
- [Define the information you want to extract](https://docs.retellai.com/features/post-call-analysis-create.md): Define Retell post-call analysis fields — boolean, selector, text, and number categories — to automatically extract structured information from every call.
- [Post-call analysis overview and categories](https://docs.retellai.com/features/post-call-analysis-overview.md): Retell post-call analysis automatically scores and structures customer calls after they end — built-in categories plus custom analysis for your workflow.
- [Register and set up a Retell webhook](https://docs.retellai.com/features/register-webhook.md): Register a Retell webhook to receive real-time call_started, call_ended, and call_analyzed events, with Node.js, Python, and signature verification code.
- [Rerun Post-Call/Chat Analysis](https://docs.retellai.com/features/rerun-call-analysis.md): Edit Retell post-call or post-chat analysis prompts and rerun processing on past sessions to regenerate summaries and success metrics with new criteria.
- [Secure the webhook](https://docs.retellai.com/features/secure-webhook.md): Verify Retell AI webhook signatures with the raw request body, X-Retell-Signature header, API key, SDK helpers, and IP allowlisting.
- [Call & chat history](https://docs.retellai.com/features/session-history.md): Browse Retell call and chat history in the dashboard: filter sessions, inspect transcripts and analysis, rerun analysis, and export to CSV.
- [Retell webhooks overview](https://docs.retellai.com/features/webhook-overview.md): Overview of Retell webhooks — call_started, call_ended, and call_analyzed events delivered to your server so you can react to call activity without polling.
- [Security and compliance](https://docs.retellai.com/general/compliance.md): Retell AI is HIPAA and GDPR compliant and SOC 2 Type 1 and Type 2 certified. Review our data handling, BAA, DPA, and GDPR erasure process.
- [Introduction to Retell](https://docs.retellai.com/general/introduction.md): Retell is a platform to build, test, deploy, and monitor AI voice and chat agents with telephony, prompts, tools, and analytics built in.
- [Retell CLI](https://docs.retellai.com/get-started/cli.md): Install the Retell CLI to manage agents, phone numbers, knowledge bases, and other Retell resources from your terminal with simple commands.
- [Create voice agent with TypeScript SDK](https://docs.retellai.com/get-started/create-agent-with-sdk.md): Create a Retell AI phone agent with the TypeScript SDK in Node.js: configure its prompt, voice, webhook, call limits, testing, and published version.
- [Retell MCP server for AI assistants](https://docs.retellai.com/get-started/mcp-server.md): Use Retell's MCP server to build and manage voice agents from MCP-capable clients like Cursor, Claude Desktop, and Claude Code via Retell APIs.
- [Build your first phone agent in 15 minutes](https://docs.retellai.com/get-started/quick-start.md): Build your first Retell AI phone agent in 15 minutes: create an account, pick a template, test in the dashboard, deploy to a phone number, and make a call.
- [Retell SDKs for TypeScript and Python](https://docs.retellai.com/get-started/sdk.md): Official Retell SDKs for Node.js and Python — typed clients, simple API key auth, structured error handling, and full coverage of voice and chat endpoints.
- [Add function calling](https://docs.retellai.com/integrate-llm/integrate-function-calling.md): Give a Retell custom LLM agent tools to book appointments, transfer to a human, press IVR digits, and end calls, all logged in the transcript.
- [Connect your LLM](https://docs.retellai.com/integrate-llm/integrate-llm.md): Stream LLM completions to a Retell voice agent over the LLM WebSocket, build prompts from the live transcript, and cancel responses Retell discards.
- [Best practices](https://docs.retellai.com/integrate-llm/llm-best-practice.md): Keep a Retell custom LLM agent fast and reliable: cut time to first sentence, write prompts for speech, control tool accuracy, and survive dropped connections.
- [Custom LLM overview](https://docs.retellai.com/integrate-llm/overview.md): Run your own LLM behind a Retell voice agent. Retell handles telephony, transcription, and turn-taking while your WebSocket server generates each reply.
- [Set up your server](https://docs.retellai.com/integrate-llm/setup-websocket-server.md): Build the LLM WebSocket server that a Retell custom LLM agent connects to: handle config and begin messages, respond to response_required events.
- [Troubleshooting](https://docs.retellai.com/integrate-llm/troubleshooting.md): Debug a Retell custom LLM integration: map error_llm_websocket disconnection reasons to fixes for silent agents, dropped calls, and WebSocket errors.
- [Give your AI agent persistent contact memory](https://docs.retellai.com/integrations/build-contact-memory.md): Map post-call analysis fields to contact fields so your Retell AI agent remembers preferences, past issues, and commitments across every conversation.
- [CRM data mappings](https://docs.retellai.com/integrations/crm-mappings.md): How data flows between your CRM, Retell contacts, and post-call analysis: inbound and outbound field mappings, sync direction, update modes, and custom fields.
- [CRM integrations](https://docs.retellai.com/integrations/crm-overview.md): Connect Salesforce or HubSpot to Retell: sync contacts both ways, map post-call analysis to contact fields, and log call and chat activity to the CRM.
- [Connect HubSpot](https://docs.retellai.com/integrations/hubspot.md): Connect HubSpot to Retell with a private app access token to sync contacts both ways, map post-call analysis to properties, and log calls to timelines.
- [Trigger Retell calls from HubSpot workflows](https://docs.retellai.com/integrations/hubspot-marketplace.md): Install and configure the Retell AI HubSpot app to trigger outbound voice agent calls from HubSpot workflows, pass contact context, and sync call results back.
- [Connect Salesforce](https://docs.retellai.com/integrations/salesforce.md): Connect Salesforce to Retell with an External Client App and OAuth 2.0 client credentials to sync contacts, update fields, and log calls as Tasks.
- [Audio Basics](https://docs.retellai.com/knowledge/audio-basics.md): Audio fundamentals for building voice AI — sampling, quantization, codecs, sample rates, and how audio is represented digitally in telephony systems.
- [Debug call transfer failure](https://docs.retellai.com/reliability/call-performance.md): Debug Retell call transfer failures — verify the `transfer_call` function is configured correctly for single, multi-prompt, and conversation flow agents.
- [Check actual latency](https://docs.retellai.com/reliability/check-actual-latency.md): Monitor per-call latency in the Retell Call History dashboard or via the Get Call API — review P50, P90, and P99 end-to-end latency to find slow calls.
- [Check estimated latency](https://docs.retellai.com/reliability/check-estimated-latency.md): View estimated end-to-end latency for a Retell agent before going live — see which turtle-icon features are pushing latency higher than expected.
- [Debug call disconnection](https://docs.retellai.com/reliability/debug-call-disconnect.md): Diagnose why a Retell call disconnected — look up the `disconnection_reason` in the dashboard or Get Call API and follow the table of causes and fixes.
- [Debug SIP calls using PCAP file](https://docs.retellai.com/reliability/debug-calls-pcap.md): Capture and analyze PCAP files in Wireshark and tshark to diagnose Retell SIP calls — codec negotiation, audio quality, one-way audio, and missed DTMF tones.
- [Debug outbound connection issues](https://docs.retellai.com/reliability/debug-outbound-call.md): Diagnose `not_connected` outbound Retell calls — work through `invalid_destination`, `no_valid_payment`, carrier blocks, and other disconnection reasons.
- [Fraud Protection](https://docs.retellai.com/reliability/fraud-protection.md): Protect your Retell deployment with rate limiting by IP and destination number, geographic restrictions, and public key fraud protection for frontend traffic.
- [Prevent abuse](https://docs.retellai.com/reliability/prevent-abuse.md): Defend Retell agents against International Revenue Sharing Fraud and other abuse — rate limit traffic, restrict destinations, and lock down public keys.
- [Reliability Overview](https://docs.retellai.com/reliability/reliability-overview.md): How Retell AI maintains 99.9% uptime with enterprise infrastructure, monitoring, fallback mechanisms, and platform resilience features.
- [Troubleshoot high latency](https://docs.retellai.com/reliability/troubleshoot-latency.md): Reduce high Retell end-to-end latency — pick a faster LLM, shorten your prompt, enable fast tier, and diagnose slow LLM, ASR, and TTS components per call.
- [Debug wrong response](https://docs.retellai.com/reliability/wrong-response.md): Fix Retell agents that give incorrect responses — switch to a more capable LLM, simplify prompt structure, add finetune examples, and review function calls.
- [Increase transcription accuracy](https://docs.retellai.com/reliability/wrong-transcript.md): Increase Retell transcription accuracy — use boosted keywords for niche terms, choose the right ASR provider, and tune transcription modes for clarity.
- [Batch test your agent](https://docs.retellai.com/test/batch-test-simulation.md): Run Retell batch tests on many simulation cases at once, then review pass rate and per-case results in Batch Testing History to catch regressions.
- [Manually test your agent](https://docs.retellai.com/test/llm-playground.md): Test a Retell agent in the LLM Playground: chat manually or with an AI-simulated user, inspect tool calls and transitions, and replay any turn.
- [Debug your agent response](https://docs.retellai.com/test/llm-playground-debug.md): Debug a Retell agent in the LLM Playground: open Debug on any response or transition, apply suggested fixes, and regenerate the turn to verify.
- [Automatically test your agent](https://docs.retellai.com/test/llm-simulation-testing.md): Test a Retell agent with LLM simulation: an AI-simulated user runs your scenario in a text conversation, and success criteria grade each run.
- [Testing overview](https://docs.retellai.com/test/test-overview.md): Compare Retell's agent testing methods — LLM Playground, simulation, batch, web call, and phone call testing — and pick the right one for each stage.
- [Phone call testing](https://docs.retellai.com/test/test-phone.md): Test a Retell voice agent on a real phone call: attach a number, place an outbound test call or dial in, and validate audio, latency, DTMF, and transfers.
- [Web call testing](https://docs.retellai.com/test/test-web.md): Test a Retell voice agent with a browser web call from the dashboard: use the Test Audio panel to hear real audio, latency, and interruptions.
- [Testing pricing](https://docs.retellai.com/test/testing-pricing.md): How Retell bills agent testing: text tests (Playground, simulation, batch) cost per message and voice tests (web, phone) cost per minute at production rates.
- [Testing with Conductor](https://docs.retellai.com/test/testing-with-conductor.md): Use Conductor, Retell's AI copilot, to generate simulation test cases from real calls, cold-start suites for new agents, and target tool calls.

## OpenAPI Specs

- [openapi-final](https://docs.retellai.com/openapi-final.yaml)
- [openapi](https://docs.retellai.com/openapi.yaml)
- [package-lock](https://docs.retellai.com/package-lock.json)
- [gen](https://docs.retellai.com/gen.yaml)
- [config](https://docs.retellai.com/config.yaml)