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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 v2.1.248 Home All releases olderv2.1.247 v2.1.250newer
Claude Code v2.1.248

MCP tool-not-found errors now say why the server is unavailable

You'll notice
Useful4 Signal2
MCP

A missing MCP tool now explains the server's state instead of just saying it doesn't exist.

What

When the model calls a missing tool whose name begins with mcp__, the error now appends a sentence explaining the server's state instead of just saying the tool does not exist. Causes covered are reconnecting, needs_auth, policy_blocked, disconnected, disabled, org_blocked, auth_completed, not_offered, denied and not_configured. This is on for everyone, with no flag involved.

Details
  • Each cause has two wordings, one for when the server is in context and one for when it is not.
  • The withdrawn cause appends nothing.
Evidence

has disconnected. Continue without this tool; it becomes callable again only if the server reconnects.

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

See this entry in the whole of v2.1.248 →