I set up a Zapier MCP server to connect VAPI to a data source to lookup client IDs. The MCP server tests correctly in Zapier but fails in VAPI, I'm not sure what the error means. 19:01:14:601[WARN] Model request failed (attempt #1, reason: (Invalid 'tools[2].function.name': string does not match pattern. Expected a string that matches the pattern '^[a-zA-Z0-9_-]+$'.)) Call ID is f0375729-2245-420d-ad39-761064ccbac8

Looking into it

from what I saw this issue is related to how VAPI names the tool. We hosted the MCP server at

Render

and the tool is named by VAPI as

onrender.maps_search_places

that

dot

in tool name causes the issue. But I could test the Agent using Gemini and it worked. However, it doesn't work with OpenAI neither Anthropic. I hope the VAPI team fixes this soon.

Rename the tool in your setup by replacing dots with underscores like onrender_maps_search_places, then update all assistant references to match. This ensures compatibility with OpenAI, Anthropic, and other LLMs that don’t support dots in tool names.

at our MCP server the tool name is

maps_search_places

, the prefix

onrender.

is added automatically by the VAPI mcp client, which we don't control.

Hey @GP, the issue is on our side and most probably it will be resolved by tomorrow US time.

Bumping this, I'm experiencing the same; would like to set up Zapier mcp servers w assistants! Seems to happen regardless of model selection

Well they want you to use the CLI instead of the GUI to get around it because you have to pull the dots out of all the tool instances. I ended up abandoning MCP for now and just using tool calls directly to a make.com endpoint using web hooks. Make.com seems to be more stable so it can just return the necessary value.

We do not permit the use of dots; however, the issue appears to originate from OpenAI. It has been observed that Zapier is returning function names containing dots, and this occurrence is limited exclusively to the Zapier MCP server.

Following

Hey Josh and GP, the issue is resolved. Please Try again and let me know how it goes. First, try the daily channel, then switch to the weekly channel. The changes are in the daily channel now and will be deployed to weekly by Saturday.

Perfect, thank you.

No worries!