You'll noticeTier: how much it should matter to you
2Useful: my rating, 1 to 5
1Signal: worth watching, 1 to 5
MCPArea: what it touches
ImprovementsKind: in v2.1.311,
ImprovementsSection of the release
Unclear It is not clear what the new check looks for in structuredContent, so which results now cause an error is unknown.
What
MCP servers are outside programs that give Claude Code extra tools. Some of them return structuredContent, which is result data in a fixed shape. After an MCP tool call, Claude Code now runs a new check on that data. When the check fails, the call ends in an error that names the MCP server and the tool. Before, there was no such check.
Why
Some MCP tool calls that used to return a result may now stop with an error instead. The error names the server and the tool, so you can tell which one to look at.
How sure we are
Something disagreesSomething we can check disagrees with this entry, or the writer said they could not settle it.
The writer flagged doubtIt is not clear what the new check looks for in structuredContent, so which results now cause an error is unknown.
