feat(contrib/mcp-go): Simplified way to add tracing

[jboolean]

What does this PR do?

Provides a simpler, more extensible, and less leaky way to add tracing to mcp-go.

Motivation

Previously I proposed a version which used reflection, but changed approaches: #4115

Reviewer's Checklist

• Changed code has unit tests for its functionality at or near 100% coverage.
• System-Tests covering this feature have been added and enabled with the va.b.c-dev version tag.
• There is a benchmark for any new code, or changes to existing code.
• If this interacts with the agent in a new way, a system test has been added.
• New code is free of linting errors. You can check this by running ./scripts/lint.sh locally.
• Add an appropriate team label so this PR gets put in the right place for the release notes.
• Non-trivial go.mod changes, e.g. adding new modules, are reviewed by @DataDog/dd-trace-go-guild.

Unsure? Have a question? Request a review!

[jboolean]

• feat(contrib/mcp-go): Simplified way to add tracing #4122 : 2 dependent PRs (#4123 , #4158 ) 👈 (View in Graphite)
• feat(contrib/mcp-go): Trace MCP session initializations with MLObs spans #4101 : 2 other dependent PRs (#4106 , #4115 )
• feat(contrib/mcp-go): Initial mcp-go tracer implementation #4100
• main

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[jboolean]

In the future (next PR in stack) a boolean option to enable intent capture will be added to this config.

[pr-commenter]

Benchmarks

Benchmark execution time: 2025-11-20 20:04:12

Comparing candidate commit 1c7172d in PR branch jb/simplified-way-to-add-tracing with baseline commit 3c75965 in branch main.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 15 metrics, 0 unstable metrics.

[datadog-official]

✅ Tests

🎉 All green!

❄️ No new flaky tests detected
🧪 All tests passed

_{This comment will be updated automatically if new data arrives.
🔗 Commit SHA: 1c7172d | Docs | Datadog PR Page | Was this helpful? Give us feedback!}

[genesor]

It would be nice to add an example and in documentation of how customer should use it with pre-existing hooks. Otherwise LGTM

[dd-devflow-routing-codex]

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2025-11-19 16:07:16 UTC ℹ️ Start processing command /merge -c

[dd-devflow-routing-codex]

View all feedbacks in Devflow UI.

2025-11-20 19:44:44 UTC ℹ️ Start processing command devflow:merge

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2025-11-20 19:44:54 UTC ℹ️ MergeQueue: waiting for PR to be ready

This pull request is not mergeable according to GitHub. Common reasons include pending required checks, missing approvals, or merge conflicts — but it could also be blocked by other repository rules or settings.
It will be added to the queue as soon as checks pass and/or get approvals.
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2025-11-20 20:07:32 UTC ℹ️ MergeQueue: merge request added to the queue

The expected merge time in main is approximately 45m (p90).

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2025-11-20 20:20:25 UTC ℹ️ MergeQueue: This merge request was merged