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Platform Setup

Connect FlowCaptain to your own voice bot platform: Retell AI, VAPI, Fonio, or other platforms.

Platform Setup

If you want to connect FlowCaptain to your own voice bot platform, here are guides for the most common platforms. The matching URLs and headers — with your calendar ID already filled in — are in the dashboard under Calendar → API → Integration Guide.

A separate voice bot platform is not required. FlowCaptain includes a built-in phone assistant: under Phone Numbers, you get a number directly from FlowCaptain and assign it to your assistant. This page is for advanced users who want to integrate FlowCaptain into existing voice bot infrastructure.

Every request needs your calendar ID. All endpoints (Autopilot, MCP, and REST) require a calendarId — as a query parameter on the MCP URL, and as a field in the JSON body for Autopilot and REST. Replace YOUR_CALENDAR_ID below with it.

Retell AI

MCP Node (Recommended)

  1. Add an MCP Node to your Retell agent
  2. URL: https://api.flowcaptain.com/mcp?calendarId=YOUR_CALENDAR_ID
  3. Header: Authorization: Bearer sk_live_your_api_key
  4. Retell discovers all FlowCaptain tools automatically — no manual function configuration needed

Autopilot via Custom Function

The calendarId belongs in the URL (query parameter), not as a function parameter — Retell wraps function parameters in an args object that the API does not read for calendarId.

  1. Add a Custom Function:
    • Name: autopilot
    • URL: https://api.flowcaptain.com/api/v1/autopilot?calendarId=YOUR_CALENDAR_ID
    • Method: POST
    • Headers: Authorization: Bearer sk_live_your_api_key
  2. Define the parameters:
    • message (string, required) — "What the caller just said"
    • sessionId (string, optional) — "Session ID from the previous response"
    • callerIdNumber (string, optional) — "Caller's phone number"
  3. System prompt:
Call the "autopilot" function on EVERY caller message.
Forward the "message" field verbatim — do not change anything.
Speak the response in the "speak" field verbatim — add nothing, omit nothing.
When "done" is true, say goodbye and end the call.
Return the "sessionId" on every call.
NEVER try to answer questions yourself.

Important agent settings: Set "Speak During Execution" to Off, "Talk After Action Completed" to On, and "Talk While Waiting" to Off. Wrong settings can cause messages not to be forwarded.

Custom Functions (individual)

Set up separate custom functions for each endpoint. Append ?calendarId=YOUR_CALENDAR_ID to every custom function URL (e.g. https://api.flowcaptain.com/api/v1/check-availability?calendarId=YOUR_CALENDAR_ID, .../book-appointment?calendarId=YOUR_CALENDAR_ID, etc.) — because of Retell's args wrapper, the calendarId must be in the URL, not the body. Requires your own system prompt for the conversation flow.

VAPI

  1. Add an MCP server tool integration to your VAPI assistant
  2. URL: https://api.flowcaptain.com/mcp?calendarId=YOUR_CALENDAR_ID
  3. Authorization header: Bearer sk_live_your_api_key
  4. VAPI discovers all tools automatically

Alternatively, you can configure individual HTTP tools for the REST endpoints — every request body must include "calendarId": "YOUR_CALENDAR_ID".

Fonio

Fonio does not support MCP. Use the API Request tool (requires Team plan) and create one tool for each action:

  • POST https://api.flowcaptain.com/api/v1/check-availability
  • POST https://api.flowcaptain.com/api/v1/book-appointment
  • POST https://api.flowcaptain.com/api/v1/cancel-appointment
  • POST https://api.flowcaptain.com/api/v1/reschedule-appointment

Every request body must include "calendarId": "YOUR_CALENDAR_ID"; use the header Authorization: Bearer sk_live_.... The complete body templates with placeholders are in your calendar's Integration Guide.

Other Platforms

Any platform that supports HTTP calls can use FlowCaptain:

  • MCP — POST https://api.flowcaptain.com/mcp?calendarId=YOUR_CALENDAR_ID for automatic tool discovery
  • Autopilot — POST https://api.flowcaptain.com/api/v1/autopilot for full conversation handling (include "calendarId": "YOUR_CALENDAR_ID" in the body)
  • REST API — Individual endpoints for availability, booking, cancellation, rescheduling (include "calendarId": "YOUR_CALENDAR_ID" in the body)

All endpoints require the header Authorization: Bearer sk_live_... and your calendar ID.

Prompt Tips for MCP/REST Users

When using MCP or individual REST endpoints, your voice bot controls the conversation flow itself. Keep in mind:

  • Natural language only for availability — Callers say "next Monday", not "2026-03-15"; for booking, your bot converts the confirmed time into an ISO timestamp
  • Confirm before booking — Always read back the time slot and get confirmation
  • Offer alternatives — FlowCaptain returns alternatives when the desired time is taken
  • Use caller ID — Pass callerIdNumber so FlowCaptain can find appointments without asking for the number over the phone
  • Never ask for phone numbers — Speech recognition has a ~70% error rate on phone numbers