MCP error -32603: failed to list pull requests: GET https://api.github.com/repos/[owner]/[repo]/pulls: 401 (Bad

MCP error -32603: failed to list pull requests: GET https://api.github.com/repos/[owner]/[repo]/pulls: 401 (Bad credentials)

TL;DR: Regenerate your GitHub personal access token and put the new value in the MCP config env block as GITHUBPERSONALACCESS_TOKEN. A 401 Bad credentials means the token itself is rejected: expired, revoked, or pasted with a typo. It is not a scope problem. Restart the MCP client after changing the token so the server picks up the new value.

The error

MCP error -32603: failed to list pull requests: GET https://api.github.com/repos/[owner]/[repo]/pulls: 401 (Bad credentials)

Fix it

1. Regenerate the token at GitHub Settings, Developer settings, Personal access tokens, and copy the new value immediately. Expected: GitHub shows the new token once; you have it on your clipboard.

2. In your MCP client config, set GITHUBPERSONALACCESS_TOKEN to the new token inside the server env block. Expected: The config file contains the new token value in the env section.

3. Restart the MCP client completely (Claude Desktop, Cursor, etc.) so the server process relaunches. Expected: The GitHub server appears in the tool list without the 401 on the next call.

4. Call a simple read tool like list pull requests again. Expected: The call returns data instead of MCP error -32603.

When this applies

Every GitHub MCP tool call fails with -32603 and the underlying cause is a 401 Bad credentials from api.github.com. The token worked before and recently stopped, or it never worked.

When this does NOT apply

If the error is a 403 (forbidden) or 404 on a specific repo, that is scopes or repo access, not credentials. If the env var is unset entirely, see the missing-token skill instead.

Tool compatibility

GitHub MCP server (modelcontextprotocol/servers), recent versions

Also seen as

• 401 Unauthorized from the GitHub API through the MCP server
• Bad credentials on every GitHub MCP tool call
• GitHub MCP server stopped working overnight with 401

Why it happens

The MCP server sends your personal access token as a Bearer token on each API call. GitHub answers 401 Bad credentials when the token is expired, manually revoked, or malformed. The server wraps the API failure as MCP error -32603, which hides the real 401 one layer down.

Edge cases

• Fine-grained PATs expire on the schedule you chose; classic PATs show as expired in the token list.
• If you use GitHub Enterprise Server, a token for github.com will 401 against your enterprise host; generate the token on the right host.
• A trailing newline pasted into the env value also 401s; paste into a plain text editor first to check.