DRAFT: Add CLIENT spans and trace context injection for vMCP backends #3684
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Add SpanKindClient spans to the vMCP telemetry backend client with standard MCP OTEL attributes (mcp.method.name, server.address, server.port as int, network.transport, gen_ai.tool.name). Add mcp.client.operation.duration histogram using shared bucket boundaries from the telemetry package. Fix error.type to use the error message instead of Go type name. Fix server.port to be int per OTEL conventions. Inject W3C Trace Context (traceparent/tracestate) into outgoing MCP tool call requests via params._meta for end-to-end distributed tracing across vMCP → backend boundaries. Addresses #3399. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
ChrisJBurns
requested review from
JAORMX,
amirejaz,
jerm-dro,
jhrozek and
yrobla
as code owners
This was referenced Feb 6, 2026
Codecov Report❌ Patch coverage is
Additional details and impacted files@@ Coverage Diff @@
## otel/standard-metrics-attributes #3684 +/- ##
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+ Coverage 66.00% 66.02% +0.01%
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Files 418 418
Lines 41348 41401 +53
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+ Hits 27293 27333 +40
- Misses 11955 11960 +5
- Partials 2100 2108 +8 ☔ View full report in Codecov by Sentry. 🚀 New features to boost your workflow:
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ChrisJBurns
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Summary
SpanKindClientspans to the vMCP telemetry backend client with standard MCP OTEL attributesmcp.client.operation.durationhistogram using sharedMCPOperationDurationBucketsfrom telemetry packageserver.portto beintper OTEL conventions (wasstring)error.typeto use error message instead of Go type name (%T)traceparent/tracestate) into outgoing MCP tool call requests viaparams._meta%winfmt.Errorf(changed to%vfor second error)Addresses #3399.
PR Stack (3/3): #3682 (propagation) → #3683 (metrics/attributes) → This PR
Test plan
go build ./...passesgo test ./pkg/vmcp/server/...passesgo test ./pkg/vmcp/client/...passestask lint-fixpasses with 0 issuesresolveServerAddrPortreturns(string, int)andattrServerPort.Int()is used🤖 Generated with Claude Code