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Documentation Index

Fetch the complete documentation index at: https://docs.retellai.com/llms.txt

Use this file to discover all available pages before exploring further.

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Overview

While we generally bill based on actual call duration, certain call characteristics may result in adjusted billing to ensure fair pricing for our services.

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Rule 1: Minimum Duration for Dynamic Opening Messages

When it applies: Calls shorter than 10 seconds that use dynamic opening messages when AI speaks first Billing adjustment: Minimum charge of 10 seconds
Dynamic Message - AI Speaks first
Example:
  • Call duration: 6 seconds
  • Dynamic opening messages: Enabled
  • Billed duration: 10 seconds (4 seconds additional charge)
Why: Dynamic opening messages require processing time regardless of call length, so we ensure a minimum charge to cover these costs.

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Rule 2: LLM Price Scaling for > 3,500 Token Prompt Length

When it applies: Agents that use more than 3,500 LLM tokens in their prompts Billing adjustment: Duration is scaled proportionally based on token usage What’s included in token calculation:
  • global prompt
  • functions (tool descriptions)
  • state / node prompt
  • transcript between agent and user
  • tool call history and results
Flex mode is a common trigger for this rule. It compiles all node prompts, transitions, and tool descriptions into a single LLM context, which can push the token count well above 3,500.
Price calculation:
  • Scaling Factor = Prompt LLM Tokens ÷ 3,500
  • Billed Duration = Original Duration × Scaling Factor (rounded up)
Example:
  • Call duration: 60 seconds
  • LLM tokens used: 4,200
  • Scaling factor: 4,200 ÷ 3,500 = 1.2
  • Billed duration: 72 seconds (12 seconds additional charge)
Long token prompts pricing in dashboard
Why: Larger LLM prompt lengths incurs greater costs due to token-based pricing from our underlying model providers, so we scale the billing accordingly to reflect these increased expenses.