Why is Chroma MCP not working in ChatGPT (Codex)?

It failed in our test on Oct 22, 2026. Errors we observed: no successful call to this server's tools; answer missing ['TP-A6A725']; no tool result containing ['TP-A6A725']; no successful call to this server's tools; answer missing ['TP-A6A725']; no tool result containing ['TP-A6A725']

Chroma MCP not working in ChatGPT (Codex)? Fixes

Failed It failed in our test on Oct 22, 2026. Below is the exact setup we used in ChatGPT (Codex) (codex-cli 0.162.0-alpha.17.2), every error we saw, and what to check, all from our own run log.

Date tested: Oct 22, 2026 · From our harness, not the maker’s claims · How we test

1. Use the install config we tested in ChatGPT (Codex)

[mcp_servers.chroma]
command = "uvx"
args = ["chroma-mcp", "--client-type", "persistent", "--data-dir", "{SANDBOX}/chroma"]

Replace any <YOUR_…> placeholder and local test paths with your own. Every client’s tested snippet is on the Chroma MCP page.

2. Check that ChatGPT (Codex) connects to it

In our run the connect check was not run. Our check output:

no tool call reached the server

Server log (stderr) we captured

Why it failed to start in Claude Code and Cursor (2026-10-19): first lines of the server's error output

Traceback (most recent call last):
  File "…/bin/chroma-mcp", line 6, in <module>
    from chroma_mcp import main
  File "…/lib/python3.12/site-packages/chroma_mcp/__init__.py", line 3, in <module>
    from .server import main
  File "…/lib/python3.12/site-packages/chroma_mcp/server.py", line 4, in <module>
    from mcp.server.fastmcp import FastMCP
  File "…/lib/python3.12/site-packages/mcp/__init__.py", line 3, in <module>
    from .server.session import ServerSession
  File "…/lib/python3.12/site-packages/mcp/server/__init__.py", line 1, in <module>
    from .fastmcp import FastMCP
  File "…/lib/python3.12/site-packages/mcp/server/fastmcp/__init__.py", line 5, in <module>
    from .server import Context, FastMCP
  File "…/lib/python3.12/site-packages/mcp/server/fastmcp/server.py", line 29, in <module>
    from mcp.server.fastmcp.tools import ToolManager
  File "…/lib/python3.12/site-packages/mcp/server/fastmcp/tools/__init__.py", line 1, in <module>
    from .base import Tool
  File "…/lib/python3.12/site-packages/mcp/server/fastmcp/tools/base.py", line 10, in <module>
    from mcp.server.fastmcp.utilities.func_metadata import FuncMetadata, func_metadata
  File "…/lib/python3.12/site-packages/mcp/server/fastmcp/utilities/func_metadata.py", line 11, in <module>
    from pydantic._internal._typing_extra import eval_type_backport
ImportError: cannot import name 'eval_type_backport' from 'pydantic._internal._typing_extra' (…/lib/python3.12/site-packages/pydantic/_internal/_typing_extra.py)

Errors we observed

agent task: roundtrip: no successful call to this server's tools; answer missing ['TP-A6A725']; no tool result containing ['TP-A6A725']
agent task: roundtrip (tool error during the run): no successful call to this server's tools; answer missing ['TP-A6A725']; no tool result containing ['TP-A6A725']

Quoted from our run log. Secrets redacted. We list only what we saw.

More help

Chroma MCP: all results and setup · Full ChatGPT (Codex) run · General ChatGPT (Codex) MCP troubleshooting