Sweep 19 Sep 2026 · 02:36Z Build v2.1.278 500 read Stable v2.1.267 Latest v2.1.278 Next v2.1.278 Feeds RSS JSON llms.txt Unofficial
Claude Code v2.1.277 ·

Tool-input JSON parse failures now log MCP status and richer Zod error detail

Tool-input JSON parse failure logs now show whether the tool was an MCP tool and give richer Zod error detail

TierUnder the hoodhow much it should matter to you
Useful1my rating, 1 to 5
Signal1worth watching, 1 to 5
AreaTool Validationwhat it touches
KindInternal Changesin v2.1.277,
Under the hood

Tool-input JSON parse failure logs now show whether the tool was an MCP tool and give richer Zod error detail

What

When Claude Code fails to parse a tool's input as JSON, the internal telemetry event tengu_tool_input_json_parse_fail now records an isMcp field noting whether the tool came from an MCP server (a way of connecting external tools to Claude Code). Related error logging for schema-normalization failures (checked with a library called Zod) now includes the tool's display name, the list of specific Zod issue codes, and the length of the error message, instead of a single flattened error string.

Why

This gives more structured detail for diagnosing why a tool call's input failed to parse, without changing what happens for the user in the moment.

See this entry in the whole of v2.1.277 →