You'll noticeTier: how much it should matter to you
3Useful: my rating, 1 to 5
1Signal: worth watching, 1 to 5
TracingArea: what it touches
ImprovementsKind: in v2.1.283,
ImprovementsSection of the release
Unclear It is not clear which built-in tools are included or exactly what differs from the previous build.
What
Tracing is an optional feature that records what Claude Code does as timed steps called spans, for use with OpenTelemetry monitoring tools. When tracing is on and a tool call succeeds, Claude Code writes the result as a tool.output attribute on the span. A tool call is one action Claude takes, such as a web search. This covers:
Results from MCP tools, which are tools provided by connected services
Results from a small set of built-in tools
Output from the account memory server is redacted. Long output is cut short and marked as truncated, with its original length recorded.
Why
If you collect tracing data, tool results may now appear in it. Keep that in mind when deciding where the data goes.
tool.outputEnvironment variablesmodified, high confidence| `OTEL_LOG_TOOL_CONTENT` | Set to `1` to include tool content in the `tool.output` OpenTelemetry span event. Span attributes carry tool content under [their own gates](/docs/en/monitoring-usage#new-context-gates). Requires [tracing](/docs…see the edit
Since it was published
The entry above is what we published on the day. These lines were added later, as Anthropic's own pages caught up, and they sit beside the original rather than replacing it.
Confirmed sinceAnthropic's documentation has since written up tool.output, on Monitoring.**`tool.output` span event on `claude_code.tool`**monitoring-usagesee the edit
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 which built-in tools are included or exactly what differs from the previous build.
Anthropic's documentation agreestool.output on Environment variables
Anthropic's release notes agreeAdded MCP tool, WebFetch and WebSearch outputs to the tool.output OpenTelemetry span event when OTEL_LOG_TOOL_CONTENT=1
