`get_tag` tool won't work on private repositories even if the sufficient permissions are granted

[orhanasan]

Describe the bug

get_tag tool won't work for private repositories, both with providing tag name and SHA of it. Tried this with both fine grained PAT tokens and also installation token generated from a GitHub app with correct permissions (Contents read - see here).

Affected version

I am currently using remote MCP server, using the endpoint https://api.githubcopilot.com/mcp/x/all/ with header: X-MCP-Toolsets: actions,context,repos,issues,pull_requests,users.

Steps to reproduce the behavior

1. Create a fine-grained PAT token which can access a private repository and uses Contents read permission.
2. Using MCP inspector, connect to remote GitHub MCP server (be sure that Authorization -using Bearer ... format- and X-MCP-Toolsets headers are populated correctly)
3. Click 'List tools' to get tool list
4. Select get_tag tool
5. Fill the arguments
6. Observe 404 Not Found

I also tested this with GitHub Rest API and that is also not working, so it might be a problem related with Rest API (and it affected GitHub MCP server since requests are forwarded to that endpoint by a conversion layer).

Expected vs actual behavior

It should return 200 response with details seen here.