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Visual Studio Code cannot authorize with FastMCP OAuth #1379
Description
Initial Checks
- I confirm that I'm using the latest version of MCP Python SDK
- I confirm that I searched for my issue in https://github.com/modelcontextprotocol/python-sdk/issues before opening this issue
Description
I reported this against FastMCP but the bug is actually in this lib, see PrefectHQ/fastmcp#1868
If you attempt to add a MCP server that supports OAuth to VSC in mcp.json with dynamic client registration, you will catch the following error inside register.py class RegistrationHandler method handle:
validation_error = 1 validation error for OAuthClientMetadata
grant_types.2
Input should be 'authorization_code' or 'refresh_token' [type=literal_error,
input_value='urn:ietf:params:oauth:grant-type:device_code',
input_type=str]
For further information visit https://errors.pydantic.dev/2.11/v/literal_error
This was the body payload from VSC:
body = {'client_name': 'Visual Studio Code', 'client_uri': 'https://code.visualstudio.com', 'grant_types': ['authorization_code', 'refresh_token', 'urn:ietf:params:oauth:grant-type:device_code'], 'response_types': ['code'], 'redirect_uris': ['https://insiders.vscode.dev/redirect', 'https://vscode.dev/redirect', 'http://localhost/', 'http://127.0.0.1/', 'http://localhost:33418/', 'http://127.0.0.1:33418/'], 'scope': 'read:data', 'token_endpoint_auth_method': 'none', 'application_type': 'native'}
Example Code
Example `.vscode/mcp.json` file:
{
"servers": {
"my-mcp-server-7574582c": {
"url": "http://localhost:5173/mcp",
"type": "http"
}
},
"inputs": []
}Python & MCP Python SDK
FastMCP version: 2.12.2
MCP version: 1.13.1
Python version: 3.11.13
Platform: Linux-5.15.167.4-microsoft-standard-WSL2-x86_64-with-glibc2.36
FastMCP root path: /workspaces/app/.venv/lib/python3.11/site-packages
Activity
automaton82 commentedon Sep 19, 2025
I opened a PR to solve this:
#1380