awake-maroonA
VAPI•6mo ago
awake-maroon

Critical: Call failure on MCP tool changes

I'm receiving the following message in the call log: Model request failed (attempt #1, reason: Invalid 'tools[2].function.name': empty string. Expected a string with minimum length 1, but got an empty string instead.)

Here's the thing: I haven't changed the MCP server between VAPI tool updates - the tool names are not missing; they're named. I've gone to the simplest version of the tool update I can:

    type: "mcp",
    server: {
      url: process.env.MCP_SERVER_URL!,
      headers: {
        "x-organization-id": organizationId,
        "x-api-token": mcpToken,
      },
    },


I'm unable to determine the cause of the error, but it does seem to be somehow related to the client.tools.create call, and what is being fed into it. Sometimes everything's fine, sometimes it's not. Sometimes it works on create, but is resolved with an update, sometimes the other way around. It's permanent until I change some config around and retry, but it's a toss-up as to whether that will work. Logs on my MCP server show valid requests and responses with tool names in the fields.

It's worth noting that this could be an off-by-one issue: I only have two tools on the MCP server right now, so tools[2] shouldn't be a valid index. Earlier, when I had four tools, it was throwing an error with tools[4]. Unless the indexing is 1-based, this is incorrect.

Any insight into what might be causing this? It's preventing our product launch. You can see a call id at c267e1fa-b92b-4948-99d5-efb377bb7c37.
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