Invalid Pydantic model generated

[JP-Ellis]

Summary

I believe that the crate_model_from_json_schema is producing invalid Pydantic models, which eventually produce a KeyError when BaseModel.model_json_schema() is called.

Background

I was troubleshooting an issue which I believe originates from within mcpadapt.

A minimal example which produces the issue is:

#!/usr/bin/env python
from mcp import StdioServerParameters
from mcpadapt.core import MCPAdapt
from mcpadapt.crewai_adapter import CrewAIAdapter

with MCPAdapt(
    StdioServerParameters(
        command="npx",
        args=["@smartbear/mcp@latest"],
        env={
            "PACT_BROKER_BASE_URL": "https://pact.example.com",
            "PACT_BROKER_TOKEN": "foobar",
        },
    ),
    CrewAIAdapter(),
):
    ...

which you can run with

$ uv venv --python 3.12
$ uv pip install mcp mcpadapt crewai websockets
$ uv run mwe.py
Traceback (most recent call last):
  File "~/mwe/mwe.py", line 6, in <module>
    with MCPAdapt(
        ^^^^^^^^^
  [...]
KeyError: '#/properties/requestResponse/properties/request'

I first thought that the MCP server was producing some malformed output, but inspecting it and it all looks fine (the below is abridged):

{
  "tools": [
    {
      "name": "contract-testing_generate_pact_tests",
      "title": "Contract Testing: Generate Pact Tests",
      "inputSchema": {
        "$schema": "http://json-schema.org/draft-07/schema#",
        "type": "object",
        "properties": {
          "language": { "type": "string" },
          "requestResponse": {
            "type": "object",
            "properties": {
              "request": {
                "type": "object",
                "properties": {
                  "filename": { "type": "string" },
                  "body": { "type": "string" }
                },
                "required": ["body"],
                "additionalProperties": false
              },
              "response": {
                "$ref": "#/properties/requestResponse/properties/request"
              }
            },
            "required": ["request", "response"],
            "additionalProperties": false
          }
        },
        "additionalProperties": false
      },
      "annotations": {
        "title": "Contract Testing: Generate Pact Tests",
        "readOnlyHint": true,
        "destructiveHint": false,
        "idempotentHint": true,
        "openWorldHint": false
      }
    }
  ]
}

I suspect that the $ref is not being appropriately transformed, though I haven't looked into it much at this stage.

Related

The following error is related:

• [BUG] RuntimeError: Failed to initialize MCP Adapter: '#/properties/data/properties/name' crewAIInc/crewAI#3101

[grll]

@JP-Ellis thanks for reporting I will have a look