What
MCP (Model Context Protocol) servers are outside programs that give Claude extra tools. Tool search is how Claude loads tools it was not given up front; tools held back this way are called deferred.
- Tool search now cleans up the query first and matches
select:with a shared pattern. - Tool search pauses regularly while scoring tools so other work can run, and cuts queries, search hints and
select:lists to set limits. - Deferral decisions now take a
nonDeferrableBuiltinslist into account, meaning some built-in tools can no longer be held back. - An MCP tool's description now differs when the model loaded it through tool search.
- When Claude waits for an MCP tool to appear, a new
connectedGraceMsoption can keep it waiting while the server is already connected. It defaults to 0. - Failed MCP servers now carry
willRetry. The message Claude sees now splits them: servers that will retry are unavailable "for now", and the session retries them in the background when you send a message, so their tools may appear later. Others stay "unavailable for this session". Claude is told to suggest asking again in a minute for the retrying ones.
Why
Large sets of MCP tools should be less likely to freeze Claude Code during a search, and Claude gives more accurate advice when a server is only temporarily unreachable.