You'll noticeTier: how much it should matter to you
3Useful: my rating, 1 to 5
2Signal: worth watching, 1 to 5
MCPArea: what it touches
ImprovementsKind: in v2.1.271,
ImprovementsSection of the release
What
claude mcp serve now advertises a listChanged tools capability and sends a tools/list_changed notification whenever the visible set of tools changes (for example after a policy-verdict refresh), using a new debounced watcher.
Tool call handling now reads the progress token (_meta/sendNotification) from the incoming request and opens a progress-tracking resource for the duration of the call.
While a long-running tool call executes, the server sends periodic notifications/progress messages ("Running for Ns") on an interval, using that progress token.
Why
MCP clients connected to Claude Code's built-in server can now stay in sync when the available tools change, and can show live progress instead of appearing stuck during slow tool calls.
How sure we are
One source agreesOne thing we can check says the same as this entry.
Anthropic's release notes agreeFixed sustained high CPU usage and repeated tool-list requests when an MCP server sends list_changed notifications in a tight loop
