Source Intelligence
Follow Discord

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 v2.1.221 Home All releases ←olderv2.1.220 v2.1.222newer→
Claude Code v2.1.221

tools/list uses the new client listTools path with retry backoff on modern servers

Under the hood
Useful2 Signal0
MCP

Tool discovery uses a newer path with retries on servers that negotiate the modern protocol; older servers are unchanged.

What

Tool discovery has a second code path for servers that negotiated the modern protocol era.

Details
  • When the connected client reports getProtocolEra?.() === "modern", discovery calls listTools with cacheMode: "refresh" and retries retryable failures with a 250/500/1000ms backoff, logging each retry.
  • Pagination overruns on that path are recorded as capped.
  • Legacy servers keep the previous paginated tools/list walk, which is what everyone gets by default.
  • The large tool-conversion body was factored out of the cached discovery function into a shared helper that both live and cached results go through.
Evidence

tools/list failed (${de(n)}); retrying in ${o}ms

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

See this entry in the whole of v2.1.221 →