64-Character Limit on Tool Names Conflicts with MCP Spec — Should Be Removed or Configurable

[jlwainwright]

Hi team 👋 — I’ve run into the following validation error when using github-mcp-server in conjunction with Claude Code CLI:

After reviewing the official Model Context Protocol (MCP) specification, I found that no 64-character limit is defined for tool names or combined identifiers. This appears to be an implementation-specific constraint within this repo.

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🔍 Problem Summary

• The github-mcp-server enforces a 64-character limit on tool names (possibly via schema validation).
• This limit is not part of the MCP spec.
• It creates friction for valid client tools (e.g. Claude Code) that generate descriptive or concatenated tool names.

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🛠 Suggestions

1. Remove or relax the 64-character limit
   Unless technically necessary, this constraint should be removed to comply with the MCP spec.

2. Make it configurable
   If the limit is required (e.g. for DB/index safety), allow it to be set via environment variable or config.

3. Document the implementation limit clearly
   Add a note in the README or a dedicated validation section to avoid confusion for tool developers.

4. Improve the error message
   Recommend clarifying that the limit is from this server, not from MCP itself:

   "Tool name exceeds 64-character limit set by github-mcp-server (not MCP spec-defined)"

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Thanks for your work on this — happy to help with a PR if the maintainers are open to adjustments!

[SamMorrowDrums]

This is entirely an implementation specific aspect of MCP host applications, and not something we control. And MCP servers do not enforce limits for this. For the moment you can rename the server in your own config to be "GitHub" or "gh" and you should be fine.

[SamMorrowDrums]

I actually answered this previously, and we can consider shortening tool names, but the fact Claude Code uses the full string the user provides as a name for the server as part of the tool names isn't something we can control for as a user can put literally anything.

We currently suggest "github".

#431 (comment)