Source Intelligence

DisclaimerUnofficial, and not affiliated with Anthropic. Nearly all of this is read straight out of what ships: npm bundles, captured prompts, published docs. Anthropic's own notes go in verbatim, marked as theirs. The rest is my reading, and every entry carries the strings behind it. If one looks wrong, vote it down and say why.

All of v2.1.119 Home All releases olderv2.1.118 v2.1.120newer
Claude Code v2.1.119

MCP Tool Name Validation

What

Claude Code now validates MCP tool names against the emerging MCP naming standard and warns about non-conforming names.

Details
  • Hard failures (tool rejected): empty names, names exceeding 128 characters, names with characters outside [A-Za-z0-9._-]
  • Soft warnings (tool registered but warning logged): names with spaces, commas, leading/trailing dashes or dots
  • Warning output references the MCP specification proposal: [SEP: Specify Format for Tool Names](https://github.com/modelcontextprotocol/modelcontextprotocol/issues/986)
  • Registration proceeds for soft warnings: "Tool registration will proceed, but this may cause compatibility issues."
Evidence

Tool name validation (search for "Tool name validation warning", "Tool name contains invalid characters", "Allowed characters are")

Strings lifted out of the shipped bundle, so the claim above can be checked against them.

See this entry in the whole of v2.1.119 →