I’m using a Vapi agent that books moves and checks availability through Google Calendar. The built-in Google Calendar Check Availability tool doesn’t work — it always returns “free” even when events are marked busy or have titles like “Move | …”. To work around that, I built a custom tool (check_abba_calendar_availability) that triggers a Zapier zap to find all calendar events containing “Move,” format them into JSON (bookedDates and count), and send that data back to Vapi. The Zap runs perfectly, finds the right events, and produces valid JSON — but Vapi never receives the results. My Zap starts with a Webhooks by Zapier → Catch Hook trigger and ends after formatting, but Zapier no longer shows a Return Custom Response option, so it can’t send data back in the same HTTP call. I need guidance on how to make Zapier return the response to Vapi or another supported method to get the booked data into the agent.

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Recommended Solution: Instead of using a Zapier webhook, connect your Vapi agent to Zapier via the Model Context Protocol (MCP) integration. This lets your agent access Google Calendar (and 7,000+ other apps) directly through Zapier's MCP server, reliably returning results to Vapi. How to set up:

plaintext
1. Go to https://mcp.zapier.com/mcp/?client=vapi and generate your MCP server URL.
2. In the Vapi Dashboard, create an MCP tool and paste the Zapier MCP URL as the `serverUrl`.
3. Add this MCP tool to your assistant and publish.

This approach bypasses the webhook response limitation and gives your agent direct access to Zapier's integrations. See: [Vapi MCP Integration Guide](https://docs.vapi.ai/tools/mcp) Source: - [Model Context Protocol (MCP) Integration](https://docs.vapi.ai/tools/mcp)

@Vapi Support Bot I keep getting an error that the agent couldn’t use the mcp tool

Thanks for your update! To help troubleshoot the MCP tool issue, could you please share the exact error message or a brief description of what happens when your agent tries to use the MCP tool? This will help identify whether it's a configuration, authentication, or protocol problem. Source: - [Model Context Protocol (MCP) Integration](https://docs.vapi.ai/tools/mcp)

Thanks for sharing the error message. To help pinpoint the issue, could you confirm whether you included your Zapier MCP server URL and the required API key (if applicable) in your MCP tool configuration in the Vapi dashboard? This detail will help determine if the connection problem is due to authentication or configuration. If you’re unsure where to check, let me know! Source: - [Model Context Protocol (MCP) Integration](https://docs.vapi.ai/tools/mcp)

@Vapi Support Bot which API key would i be using in the mcp tool configuration

You do not need to provide a separate API key for Zapier MCP in your Vapi MCP tool configuration. The authentication is handled by the MCP server URL itself. Just use the URL you generated from Zapier as the `serverUrl`:

json
{
  "type": "mcp",
  "server": {
    "url": "https://mcp.zapier.com/api/mcp/s/your-unique-id/mcp"
  }
}

No additional API key is required—ensure the URL is complete and kept secure. See: [Vapi MCP Integration Guide](https://docs.vapi.ai/tools/mcp) Source: - [Model Context Protocol (MCP) Integration](https://docs.vapi.ai/tools/mcp)

@Vapi Support Bot yes i put mine in the server url server settings

Thanks for confirming you set the Zapier MCP server URL. To help narrow down the issue, could you please try opening your MCP server URL (the one you pasted in Vapi) in your browser or with a tool like

curl

? Does it load, or do you get an error? This will help determine if the URL is accessible from your network. Source: - [Model Context Protocol (MCP) Integration](https://docs.vapi.ai/tools/mcp)

@Vapi Support Bot it loads and returns :{"jsonrpc":"2.0","id":null,"error":{"code":-32600,"message":"Missing or invalid OAuth authorization"}}

To resolve the "Missing or invalid OAuth authorization" error: Go to [https://mcp.zapier.com/mcp/?client=vapi](https://mcp.zapier.com/mcp/?client=vapi), connect your Google Calendar account through Zapier's authentication flow, and authorize access when prompted. After completing the OAuth process, generate a new MCP server URL and update your Vapi MCP tool configuration with this new URL. This will ensure your agent can access Google Calendar via Zapier MCP without authentication errors. Example:

json
{
  "type": "mcp",
  "server": {
    "url": "https://mcp.zapier.com/api/mcp/s/your-new-id/mcp"
  }
}

Try this and your Vapi agent should be able to use the MCP tool successfully. Source: - [Model Context Protocol (MCP) Integration](https://docs.vapi.ai/tools/mcp)

@yahu I have solutions to your issues but this time its with make.com not zapier.. Everything works perfectly fine with this.. https://cdn.discordapp.com/attachments/1429280531916525689/1429356196065972297/make_appt.png?ex=68f5d731&is=68f485b1&hm=543cf1ab5a56f69d750b61b6fc57cb5bf837338ba0bc8c3795107a59e68dac27&

@GIDEON thank you, i figured out what was wrong with the MCP tool and got the scheduling to work, however now sometimes the AI ends up being silent for long periods of time and takes very long pauses for some reason.

Have you checked the start speaking plan on your vapi dashboard to see how long the timer shows.

Hi, could you please provide a call id where you experienced this issue? We would like to review the logs to identify the cause.