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… keys The adapters previously routed non-object tool arguments/results to vendor flue.tool.call.* fallback keys, on a reading of the GenAI semconv as object-shaped-only. At the pinned revision the spec types these attributes `any`: instrumentations SHOULD best-effort deserialize serialized strings, and on spans the value MAY be recorded as a JSON string when a structured format is not supported — which is the case for every OTel span attribute store. Since objects were already JSON-stringified at emission, the fork changed nothing but the key, and consumers that read the semconv keys (Sentry's AI views among them) never saw tool results: most tools — including every MCP tool — return strings. Both backends now always record under gen_ai.tool.call.*, with best-effort JSON deserialization of string payloads per the spec guidance. The flue.tool.call.* keys are removed (extension revision 5). Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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Summary
gen_ai.tool.call.*for every payload shape; drop theflue.tool.call.*fallback keys (FLUE_TELEMETRY_EXTENSION_REVISION→ 5).@flue/opentelemetryREADME and the ecosystem docs page.Why
Fixes #568. String tool results — every MCP tool, most local tools — landed on vendor keys no backend reads, so consumers of the semconv keys showed tool inputs with no outputs. The spec types these attributes
anyand sanctions JSON-string form on spans; the adapters already stringify objects, so the object-only fork changed nothing but the key.Considered and skipped: dual-writing
flue.tool.call.*for a deprecation window. Both keys draw from the same per-span content pool (sized against workerd's 64 KiB span-attribute cap), so duplicating the largest payloads in the system would make truncation kick in twice as early. Easy to switch if you'd rather keep a compat window.Verification
pnpm exec turbo run build --filter=@flue/runtime --filter=@flue/opentelemetry— passpnpm -w exec tsc --noEmit -p packages/runtime/-p packages/opentelemetry— cleanbiome linton the four changed source files — clean (@flue/runtimehas no vitest files to run)'hello'records as-is ongen_ai.tool.call.result;'{"a":1}'and{a: 1}record structuredexecute_toolspan (MCP tools included) carriesgen_ai.tool.call.resultand renders in the AI trace views🤖 Generated with Claude Code