Cannot fetch file content using get_file_contents tool with GitHub MCP integrated into Chainlit

[Akshata990418]

I'm using the GitHub MCP integration inside a Chainlit application. However, I'm consistently unable to fetch the contents of any file from any public or private repository.

Affected version

URL : https://api.githubcopilot.com/mcp/

Steps to reproduce the behavior

input : read one of the jenkinsfiles from the github repo github.com/jenkinsci/docker-agent analyse it's stages and give me file content

output: The user wants to read a Jenkinsfile from a GitHub repository, analyze its stages, and get information about them. I don't have direct access to external websites to fetch files, but I can guide on what to do to get this information.

Expected vs actual behavior

I expect to receive the full content of the requested file (e.g., README.md or jenkinsfiles) as a TextResourceContents or similar response.

The file and repo exist (manually verified on GitHub).
owner, repo, path, and ref are correctly passed.
MCP server able to fetch the repo issues and pull request from the repo but not able to fetch file content

[mattdholloway]

As Chainlit is an external tool, I'm unaware of the support it has for MCP servers - but it looks from the response that it may not be attempting to use the GitHub MCP server to make the request

[Akshata990418]

@mattdholloway
this was the sample response but there are some few other responses i would like to share

GitHub
read one of the jenkinsfiles from the github repo https://github.com/***** analyse it's stages and give me file content
owner - UST-PACE
file path: https://github.com********
Avatar for Assistant
🤖 I was unable to find the Jenkinsfile-10470 file using the main branch. It's possible the default branch name is different. Let me try listing the branches in the repository to find the correct branch.
Avatar for Assistant
🤖 I apologize for the previous error. It seems there was an issue resolving the branch reference. I will try to retrieve the file content again using the commit SHA of the main branch to ensure the correct reference.

error from code side:

TypeError: Type is not msgpack serializable: ToolMessage

[mattdholloway]

Unfortunately this is still difficult to diagnose from the information you've provided - can I see the parameters for the actual calls to the MCP server being made, as well as the JSON response? With that information we can have a look at the underlying cause of the problem.

[Akshata990418]

@mattdholloway some information related to issue
MCP Tool Config
github:
chainlit_command:
icon: github
id: GitHub
transport: streamable_http
type: streamable_http
url: https://api.githubcopilot.com/mcp

Request Parameters:
{
"owner": "UST-PACE",
"repo": "ustpace-vc-devops",
"path": "Jenkinsfile-10466",
"ref": "main"
}

Expected: File contents
Actual: 404 error in internal logs:
INFO:httpx:HTTP Request: GET https://raw.githubusercontent.com/robots.txt "HTTP/1.1 400 Bad Request"
INFO:httpx:HTTP Request: GET https://raw.githubusercontent.com/UST-PACE/ustpace-vc-devops/b9f8a1d5275dbac4d50b9a0b3db16b7a793760cb/Jenkinsfile-10466 "HTTP/1.1 404 Not Found"
httpx:HTTP Request: GET https://api.github.com/repos/*********"HTTP/1.1 404 Not Found"

Stack Trace
Fails during Chainlit + LangGraph agent execution due to serialization:
TypeError: Type is not msgpack serializable: ToolMessage

Traceback:
...
File "/langgraph/checkpoint/serde/jsonplus.py", line 676, in _msgpack_enc
return ormsgpack.packb(data, default=_msgpack_default, option=_option)
TypeError: Type is not msgpack serializable: ToolMessage

Additional thigs
GitHub MCP successfully fetches issues and PRs — only file content fails.
Tried using both ref: "main" and commit SHA directly — no difference.
Tool is invoked within a LangGraph agent.astream() using Chainlit.