You'll noticeTier: how much it should matter to you
2Useful: my rating, 1 to 5
1Signal: worth watching, 1 to 5
HooksArea: what it touches
ImprovementsKind: in v2.1.321,
ImprovementsSection of the release
What
A hook is an action Claude Code runs automatically at set points, and an mcp_tool hook does this by calling a tool from an MCP server, an outside program that provides tools. These hooks now run an extra check for refusals specific to the tool. When the tool's result or message is too large, the hook reports an error saying it gave no verdict and that the tool must send a smaller answer if this keeps happening.
Why
An oversized result now leads to a clear outcome, where the hook makes no decision and explains why, instead of a bare error.
How sure we are
One source agreesOne thing we can check says the same as this entry.
Anthropic's release notes agreeFixed PreToolUse mcp_tool hooks on stdio and HTTP MCP servers being skipped when their answer was over 16 MiB; the tool call is now refused
