{"version":"2.1.283","anchor":"mcp-and-selected-tool-outputs-recorded-on-tracing-spans","canonical_anchor":"mcp-and-selected-tool-outputs-recorded-on-tracing-spans","heading":"Tracing can record MCP and some built-in tool results as tool.output","tier":"notice","area":"Tracing","url":"https:\/\/changelogs.core-directive.com\/v\/2.1.283\/e\/mcp-and-selected-tool-outputs-recorded-on-tracing-spans","release_url":"https:\/\/changelogs.core-directive.com\/v\/2.1.283","markdown":"### Tracing can record MCP and some built-in tool results as tool.output\n\nWhen tracing is on, results from MCP tools and some built-in tools are stored on tracing spans as tool.output, with account memory redacted\n\n**Unclear.** It is not clear which built-in tools are included or exactly what differs from the previous build.\n\n**What**\n\nTracing 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:\n\n- Results from MCP tools, which are tools provided by connected services\n\n- Results from a small set of built-in tools\n\nOutput from the account memory server is redacted. Long output is cut short and marked as truncated, with its original length recorded.\n\n**Why**\n\nIf you collect tracing data, tool results may now appear in it. Keep that in mind when deciding where the data goes.\n\n- Area: Tracing\n- Names: `tool.output`\n- Tier: You'll notice\n- Useful: 3\/5\n- Signal: 1\/5"}