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The [END_CALL] tag tells the engine to end the call after Claude has finished speaking. The agent says its goodbye line first, then the call is terminated.

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Syntax

[END_CALL]
No parameters. Place it anywhere in Claude’s reply.

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Example

Caller: “Great, thanks for the help.” Agent: “You’re welcome. Have a lovely day. [END_CALL]”
The caller hears the goodbye. Then the engine ends the call cleanly.

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When to use it

Tell Claude in the system prompt when it should end calls: 
ACTIONS
- End the call when the booking is complete and confirmed: [END_CALL]
- End the call when the caller says goodbye or signals they're done: [END_CALL]
- End the call if the caller is being abusive after one warning: [END_CALL]

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Behaviour

When the engine sees [END_CALL]:
  1. The remaining text in Claude’s response is spoken to the caller
  2. The engine waits for the TTS audio to finish playing
  3. Twilio hangs up the call
  4. Post-call processing runs (recording saved, summary generated, webhook fired)
The call ends gracefully — no abrupt cutoff mid-word.

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Other ways calls end

[END_CALL] is the graceful option. Calls also end automatically when:
  • Caller hangs up — no action needed; the call object is marked ended_by: caller
  • Silence timeout — caller is silent for silence_hangup_seconds (default 30s)
  • Max duration — max_call_duration_seconds hard cap is hit (default 300s)
  • Voicemail detected on outbound calls — engine hangs up immediately
  • Error — provider failure; the engine ends safely and logs the cause
The ended_reason field on the call record tells you which one fired.
If you want the agent to confirm the booking back to the caller before ending, write that into the prompt. Claude will speak the confirmation, then emit [END_CALL].