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feat(contrib/mcp): tag server spans with client info - #5842

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feat(contrib/mcp): tag server spans with client info#5842
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max.zhang/mcp-client-info

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@mz1119 mz1119 commented Nov 6, 2026 •
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What does this PR do?

Tags MCP server initialize and tool call spans with the calling client's self-reported identity: mcp_client_name, mcp_client_title, mcp_client_version. Applies to modelcontextprotocol/go-sdk and mark3labs/mcp-go.

  • Tool calls read the identity from the request's _meta (io.modelcontextprotocol/clientInfo, sent on every 2026-07-28 request), then fall back to the session's initialize handshake.
  • Reads _meta and the session through fields that exist in the pinned SDKs (go-sdk v1.4.1, mcp-go v0.42.0), so no version changes. Newer SDKs get the same tags.
  • Values are capped at 256 characters, since they are client-supplied and repeated on every tool call span. Shared helpers: instrmcp.ClientInfoTags, instrmcp.ClientInfoTagsFromValue.
  • Existing client_name and client_version tags on initialize spans are unchanged.

Known limitations:

  • A stateless server keeps no handshake, so older-protocol tool calls there get no mcp_client_* tags.
  • mcp-go before v1 keeps the handshake only on stdio and SSE sessions, not streamable HTTP. Its Implementation has no title.

Motivation

Previously only the initialize span had client info, so tool calls could only be tied to a client by joining on mcp_session_id, which stateless servers do not have. This matches dd-trace-py #21189 and #21190.

Tested on the pinned SDKs and locally on go-sdk v1.8.0 and mcp-go v1.5.0.

🤖 Generated with Claude Code

@github-actions github-actions Bot added the apm:ecosystem contrib/* related feature requests or bugs label Nov 6, 2026
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Config Audit

PACKAGE: contrib/cloud.google.com/go/pubsubtrace
  STATUS      CONFIG                                            CALL_SITES
  UNMIGRATED  DD_GOOGLE_CLOUD_PUBSUB_PROPAGATION_AS_SPAN_LINKS  1

PACKAGE: contrib/confluentinc/confluent-kafka-go/kafkatrace
  STATUS      CONFIG                            CALL_SITES
  UNMIGRATED  DD_TRACE_KAFKA_ANALYTICS_ENABLED  1

PACKAGE: crashtracker
  STATUS      CONFIG                    CALL_SITES
  STILL_READ  DD_API_KEY                1
  STILL_READ  DD_SITE                   1
  STILL_READ  DD_TAGS                   1
  UNMIGRATED  DD_CRASHTRACKING_ENABLED  1

PACKAGE: ddtrace/opentelemetry/log
  STATUS      CONFIG                    CALL_SITES
  STILL_READ  DD_ENV                    1
  STILL_READ  DD_SERVICE                1
  STILL_READ  DD_TAGS                   1
  STILL_READ  DD_TRACE_REPORT_HOSTNAME  1
  STILL_READ  DD_VERSION                1
  UNMIGRATED  DD_HOSTNAME               1
  UNMIGRATED  OTEL_RESOURCE_ATTRIBUTES  1
  UNMIGRATED  OTEL_SERVICE_NAME         1

PACKAGE: ddtrace/opentelemetry/metric
  STATUS      CONFIG                    CALL_SITES
  STILL_READ  DD_ENV                    1
  STILL_READ  DD_METRICS_OTEL_ENABLED   1
  STILL_READ  DD_SERVICE                1
  STILL_READ  DD_TAGS                   1
  STILL_READ  DD_TRACE_REPORT_HOSTNAME  1
  STILL_READ  DD_VERSION                1
  STILL_READ  OTEL_METRICS_EXPORTER     1
  UNMIGRATED  DD_HOSTNAME               1
  UNMIGRATED  OTEL_RESOURCE_ATTRIBUTES  1
  UNMIGRATED  OTEL_SERVICE_NAME         1

PACKAGE: ddtrace/tracer
  STATUS      CONFIG                                    CALL_SITES
  STILL_READ  DD_TRACE_PROPAGATION_BEHAVIOR_EXTRACT     1
  STILL_READ  DD_TRACE_PROPAGATION_EXTRACT_FIRST        1
  STILL_READ  DD_TRACE_PROPAGATION_STYLE_EXTRACT        1
  STILL_READ  DD_TRACE_PROPAGATION_STYLE_INJECT         1
  UNMIGRATED  DD_APM_TRACING_ENABLED                    1
  UNMIGRATED  DD_TRACE_128_BIT_TRACEID_LOGGING_ENABLED  1
  UNMIGRATED  DD_TRACE_DEBUG_SEELOG_WORKAROUND          1
  UNMIGRATED  OTEL_TRACES_SAMPLER_ARG                   1

PACKAGE: instrumentation
  STATUS      CONFIG                                       CALL_SITES
  STILL_READ  DD_DATA_STREAMS_ENABLED                      1
  UNMIGRATED  DD_API_SECURITY_ENDPOINT_COLLECTION_ENABLED  1

PACKAGE: instrumentation/graphql
  STATUS      CONFIG                             CALL_SITES
  UNMIGRATED  DD_TRACE_GRAPHQL_ERROR_EXTENSIONS  1

PACKAGE: instrumentation/httptrace
  STATUS      CONFIG                                                 CALL_SITES
  UNMIGRATED  DD_GOOGLE_CLOUD_PUBSUB_PROPAGATION_AS_SPAN_LINKS       1
  UNMIGRATED  DD_HTTP_SERVER_TAG_QUERY_STRING_SIZE                   1
  UNMIGRATED  DD_TRACE_BAGGAGE_TAG_KEYS                              1
  UNMIGRATED  DD_TRACE_CLIENT_IP_ENABLED                             1
  UNMIGRATED  DD_TRACE_HTTP_SERVER_ERROR_STATUSES                    1
  UNMIGRATED  DD_TRACE_HTTP_URL_QUERY_STRING_ALLOWLIST               1
  UNMIGRATED  DD_TRACE_HTTP_URL_QUERY_STRING_ALLOWLIST_CLIENT        1
  UNMIGRATED  DD_TRACE_HTTP_URL_QUERY_STRING_ALLOWLIST_SERVER        1
  UNMIGRATED  DD_TRACE_HTTP_URL_QUERY_STRING_DISABLED                1
  UNMIGRATED  DD_TRACE_INFERRED_PROXY_SERVICES_ENABLED               1
  UNMIGRATED  DD_TRACE_OBFUSCATION_QUERY_STRING_REGEXP               2
  UNMIGRATED  DD_TRACE_RESOURCE_RENAMING_ALWAYS_SIMPLIFIED_ENDPOINT  1
  UNMIGRATED  DD_TRACE_RESOURCE_RENAMING_ENABLED                     1

PACKAGE: instrumentation/internal/namingschema
  STATUS      CONFIG                                             CALL_SITES
  STILL_READ  DD_SERVICE                                         1
  UNMIGRATED  DD_TRACE_REMOVE_INTEGRATION_SERVICE_NAMES_ENABLED  1

PACKAGE: internal
  STATUS      CONFIG                         CALL_SITES
  STILL_READ  DD_AGENT_HOST                  1
  STILL_READ  DD_TAGS                        1
  STILL_READ  DD_TRACE_AGENT_PORT            1
  STILL_READ  DD_TRACE_AGENT_URL             1
  UNMIGRATED  DD_EXTERNAL_ENV                1
  UNMIGRATED  DD_GIT_COMMIT_SHA              1
  UNMIGRATED  DD_GIT_REPOSITORY_URL          1
  UNMIGRATED  DD_TRACE_GIT_METADATA_ENABLED  1

PACKAGE: internal/appsec
  STATUS      CONFIG           CALL_SITES
  UNMIGRATED  DD_APPSEC_RULES  1

PACKAGE: internal/appsec/config
  STATUS      CONFIG                                                CALL_SITES
  UNMIGRATED  DD_API_SECURITY_DOWNSTREAM_BODY_ANALYSIS_SAMPLE_RATE  1
  UNMIGRATED  DD_API_SECURITY_ENABLED                               1
  UNMIGRATED  DD_API_SECURITY_MAX_DOWNSTREAM_REQUEST_BODY_ANALYSIS  1
  UNMIGRATED  DD_API_SECURITY_PROXY_SAMPLE_RATE                     1
  UNMIGRATED  DD_API_SECURITY_REQUEST_SAMPLE_RATE                   1
  UNMIGRATED  DD_API_SECURITY_SAMPLE_DELAY                          1
  UNMIGRATED  DD_APM_TRACING_ENABLED                                1
  UNMIGRATED  DD_APPSEC_AGENTIC_ONBOARDING                          1
  UNMIGRATED  DD_APPSEC_DISABLE_FEATURES                            1
  UNMIGRATED  DD_APPSEC_ENABLED                                     2
  UNMIGRATED  DD_APPSEC_MAX_STACK_TRACE_DEPTH                       1
  UNMIGRATED  DD_APPSEC_RASP_ENABLED                                1
  UNMIGRATED  DD_APPSEC_RULES                                       1
  UNMIGRATED  DD_APPSEC_SCA_ENABLED                                 1
  UNMIGRATED  DD_APPSEC_STACK_TRACE_ENABLED                         1
  UNMIGRATED  DD_APPSEC_TRACE_RATE_LIMIT                            1
  UNMIGRATED  DD_APPSEC_WAF_TIMEOUT                                 1

PACKAGE: internal/bazel
  STATUS      CONFIG                                  CALL_SITES
  UNMIGRATED  DD_TEST_OPTIMIZATION_MANIFEST_FILE      1
  UNMIGRATED  DD_TEST_OPTIMIZATION_PAYLOADS_IN_FILES  1

PACKAGE: internal/civisibility/envconfig
  STATUS      CONFIG                   CALL_SITES
  STILL_READ  DD_CIVISIBILITY_ENABLED  1

PACKAGE: internal/civisibility/integrations
  STATUS      CONFIG                                               CALL_SITES
  STILL_READ  DD_SERVICE                                           1
  STILL_READ  DD_TRACE_DEBUG                                       1
  UNMIGRATED  DD_CIVISIBILITY_CODE_COVERAGE_REPORT_UPLOAD_ENABLED  1
  UNMIGRATED  DD_CIVISIBILITY_DYNAMIC_ATR_BUCKETS                  1
  UNMIGRATED  DD_CIVISIBILITY_DYNAMIC_ATR_ENABLED                  1
  UNMIGRATED  DD_CIVISIBILITY_EARLY_FLAKE_DETECTION_ENABLED        1
  UNMIGRATED  DD_CIVISIBILITY_EARLY_FLAKE_DETECTION_MAX_RETRIES    1
  UNMIGRATED  DD_CIVISIBILITY_FLAKY_RETRY_COUNT                    1
  UNMIGRATED  DD_CIVISIBILITY_FLAKY_RETRY_ENABLED                  1
  UNMIGRATED  DD_CIVISIBILITY_GIT_UPLOAD_ENABLED                   1
  UNMIGRATED  DD_CIVISIBILITY_IMPACTED_TESTS_DETECTION_ENABLED     1
  UNMIGRATED  DD_CIVISIBILITY_SUBTEST_FEATURES_ENABLED             1
  UNMIGRATED  DD_CIVISIBILITY_TOTAL_FLAKY_RETRY_COUNT              1
  UNMIGRATED  DD_TEST_MANAGEMENT_ATTEMPT_TO_FIX_RETRIES            1
  UNMIGRATED  DD_TEST_MANAGEMENT_ENABLED                           1

PACKAGE: internal/civisibility/integrations/gotesting
  STATUS      CONFIG                                                           CALL_SITES
  UNMIGRATED  DD_CIVISIBILITY_INTERNAL_PARALLEL_EARLY_FLAKE_DETECTION_ENABLED  2
  UNMIGRATED  DD_CIVISIBILITY_RETRY_EXECUTION_MODE                             1
  UNMIGRATED  DD_CIVISIBILITY_RETRY_PROCESS_MAX_CONCURRENCY                    1
  UNMIGRATED  DD_CIVISIBILITY_RETRY_PROCESS_TIMEOUT                            1
  UNMIGRATED  DD_TEST_MANAGEMENT_ENABLED                                       2

PACKAGE: internal/civisibility/integrations/logs
  STATUS      CONFIG                        CALL_SITES
  UNMIGRATED  DD_CIVISIBILITY_LOGS_ENABLED  1

PACKAGE: internal/civisibility/utils
  STATUS      CONFIG                              CALL_SITES
  STILL_READ  DD_SERVICE                          1
  UNMIGRATED  DD_ACTION_EXECUTION_ID              1
  UNMIGRATED  DD_PIPELINE_EXECUTION_ID            1
  UNMIGRATED  DD_TEST_OPTIMIZATION_ENV_DATA_FILE  1
  UNMIGRATED  DD_TEST_SESSION_NAME                1

PACKAGE: internal/civisibility/utils/net
  STATUS      CONFIG                             CALL_SITES
  STILL_READ  DD_API_KEY                         1
  STILL_READ  DD_CIVISIBILITY_AGENTLESS_ENABLED  1
  STILL_READ  DD_CIVISIBILITY_AGENTLESS_URL      1
  STILL_READ  DD_ENV                             1
  STILL_READ  DD_SERVICE                         1
  STILL_READ  DD_SITE                            1
  STILL_READ  DD_TAGS                            1
  STILL_READ  DD_VERSION                         1
  UNMIGRATED  DD_CODE_COVERAGE_FLAGS             1

PACKAGE: internal/civisibility/utils/telemetry
  STATUS      CONFIG                                         CALL_SITES
  UNMIGRATED  DD_CIVISIBILITY_AUTO_INSTRUMENTATION_PROVIDER  1

PACKAGE: internal/clientip
  STATUS      CONFIG                     CALL_SITES
  UNMIGRATED  DD_TRACE_CLIENT_IP_HEADER  1

PACKAGE: internal/globalconfig
  STATUS      CONFIG                           CALL_SITES
  UNMIGRATED  DD_INSTRUMENTATION_INSTALL_ID    1
  UNMIGRATED  DD_INSTRUMENTATION_INSTALL_TIME  1
  UNMIGRATED  DD_INSTRUMENTATION_INSTALL_TYPE  1

PACKAGE: internal/hostname
  STATUS      CONFIG       CALL_SITES
  UNMIGRATED  DD_HOSTNAME  1

PACKAGE: internal/namingschema
  STATUS      CONFIG                                             CALL_SITES
  UNMIGRATED  DD_TRACE_REMOVE_INTEGRATION_SERVICE_NAMES_ENABLED  1

PACKAGE: internal/processtags
  STATUS      CONFIG                                          CALL_SITES
  UNMIGRATED  DD_EXPERIMENTAL_PROPAGATE_PROCESS_TAGS_ENABLED  1

PACKAGE: internal/remoteconfig
  STATUS      CONFIG                                  CALL_SITES
  STILL_READ  DD_ENV                                  1
  UNMIGRATED  DD_RC_TUF_ROOT                          1
  UNMIGRATED  DD_REMOTE_CONFIGURATION_ENABLED         1
  UNMIGRATED  DD_REMOTE_CONFIG_POLL_INTERVAL_SECONDS  1

PACKAGE: internal/telemetry
  STATUS      CONFIG                                             CALL_SITES
  STILL_READ  DD_API_KEY                                         1
  STILL_READ  DD_SITE                                            1
  UNMIGRATED  DD_API_SECURITY_ENDPOINT_COLLECTION_MESSAGE_LIMIT  1
  UNMIGRATED  DD_INSTRUMENTATION_TELEMETRY_ENABLED               1
  UNMIGRATED  DD_TELEMETRY_DEBUG                                 1
  UNMIGRATED  DD_TELEMETRY_DEPENDENCY_COLLECTION_ENABLED         1
  UNMIGRATED  DD_TELEMETRY_EXTENDED_HEARTBEAT_INTERVAL           1
  UNMIGRATED  DD_TELEMETRY_HEARTBEAT_INTERVAL                    1
  UNMIGRATED  DD_TELEMETRY_LOG_COLLECTION_ENABLED                1
  UNMIGRATED  DD_TELEMETRY_METRICS_ENABLED                       1

PACKAGE: openfeature
  STATUS      CONFIG                                                     CALL_SITES
  STILL_READ  DD_ENV                                                     2
  STILL_READ  DD_SERVICE                                                 2
  STILL_READ  DD_VERSION                                                 2
  UNMIGRATED  DD_EXPERIMENTAL_FLAGGING_PROVIDER_SPAN_ENRICHMENT_ENABLED  1
  UNMIGRATED  DD_FLAGGING_EVALUATION_COUNTS_ENABLED                      1

PACKAGE: profiler
  STATUS      CONFIG                                    CALL_SITES
  STILL_READ  DD_API_KEY                                1
  STILL_READ  DD_ENV                                    1
  STILL_READ  DD_SERVICE                                1
  STILL_READ  DD_SITE                                   1
  STILL_READ  DD_TAGS                                   1
  STILL_READ  DD_TRACE_STARTUP_LOGS                     1
  STILL_READ  DD_VERSION                                1
  UNMIGRATED  DD_PROFILING_AGENTLESS                    1
  UNMIGRATED  DD_PROFILING_DEBUG_COMPRESSION_SETTINGS   1
  UNMIGRATED  DD_PROFILING_DELTA                        1
  UNMIGRATED  DD_PROFILING_ENABLED                      3
  UNMIGRATED  DD_PROFILING_ENDPOINT_COUNT_ENABLED       1
  UNMIGRATED  DD_PROFILING_EXECUTION_TRACE_ENABLED      1
  UNMIGRATED  DD_PROFILING_EXECUTION_TRACE_LIMIT_BYTES  1
  UNMIGRATED  DD_PROFILING_EXECUTION_TRACE_PERIOD       1
  UNMIGRATED  DD_PROFILING_FLUSH_ON_EXIT                1
  UNMIGRATED  DD_PROFILING_OUTPUT_DIR                   1
  UNMIGRATED  DD_PROFILING_UPLOAD_TIMEOUT               1
  UNMIGRATED  DD_PROFILING_URL                          1

@datadog-prod-us1-3

datadog-prod-us1-3 Bot commented Nov 6, 2026 •
edited by datadog-datadog-prod-us1 Bot
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Pipelines  Tests

🎉 All green!

🧪 All tests passed
❄️ No new flaky tests detected

🎯 Code Coverage (details)
• Patch Coverage: 95.74%
• Overall Coverage: 73.52% (-0.14%)

This comment will be updated automatically if new data arrives.
🔗 Commit SHA: 9f4ce67 | Docs | View more details | Give us feedback!

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pr-commenter Bot commented Nov 6, 2026 •
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Benchmarks

Benchmark execution time: 2026-11-10 02:59:40

Comparing candidate commit 9f4ce67 in PR branch max.zhang/mcp-client-info with baseline commit fd44688 in branch main.

📊 Benchmarking dashboard

Found 0 performance improvements and 0 performance regressions! Performance is the same for 415 metrics, 1 unstable metrics.

Explanation

This is an A/B test comparing a candidate commit's performance against that of a baseline commit. Performance changes are noted in the tables below as:

  • 🟩 = significantly better candidate vs. baseline
  • 🟥 = significantly worse candidate vs. baseline

We compute a confidence interval (CI) over the relative difference of means between metrics from the candidate and baseline commits, considering the baseline as the reference.

If the CI is entirely outside the configured SIGNIFICANT_IMPACT_THRESHOLD (or the deprecated UNCONFIDENCE_THRESHOLD), the change is considered significant.

Feel free to reach out to #apm-benchmarking-platform on Slack if you have any questions.

More details about the CI and significant changes

You can imagine this CI as a range of values that is likely to contain the true difference of means between the candidate and baseline commits.

CIs of the difference of means are often centered around 0%, because often changes are not that big:

---------------------------------(------|---^--------)-------------------------------->
                              -0.6%    0%  0.3%     +1.2%
                                 |          |        |
         lower bound of the CI --'          |        |
sample mean (center of the CI) -------------'        |
         upper bound of the CI ----------------------'

As described above, a change is considered significant if the CI is entirely outside the configured SIGNIFICANT_IMPACT_THRESHOLD (or the deprecated UNCONFIDENCE_THRESHOLD).

For instance, for an execution time metric, this confidence interval indicates a significantly worse performance:

----------------------------------------|---------|---(---------^---------)---------->
                                       0%        1%  1.3%      2.2%      3.1%
                                                  |   |         |         |
       significant impact threshold --------------'   |         |         |
                      lower bound of CI --------------'         |         |
       sample mean (center of the CI) --------------------------'         |
                      upper bound of CI ----------------------------------'

Unstable benchmarks

These benchmarks have a confidence interval too wide to call a change; treat them as noise rather than signal.

scenario:BenchmarkContextWithSpan/detach-no-snapshot

  • unstable execution_time [-1.372ns; +1.814ns] or [-4.713%; +6.232%]

@dd-octo-sts dd-octo-sts Bot mentioned this pull request Nov 9, 2026
Open
@mz1119 @claude
feat(contrib/mcp): tag server spans with client info
88bc236 
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
@mz1119
mz1119 force-pushed the max.zhang/mcp-client-info branch from b3c972f to 88bc236 Compare November 9, 2026 19:25
@mz1119
mz1119 changed the base branch from max.zhang/mcp-stateless-sdk-support to main November 9, 2026 19:25
@mz1119
mz1119 marked this pull request as ready for review November 9, 2026 20:10
@mz1119
mz1119 requested review from a team as code owners November 9, 2026 20:10
@mz1119
mz1119 requested review from rarguelloF and removed request for a team November 9, 2026 20:10
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chatgpt-codex-connector Bot commented Nov 9, 2026 •
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Codex Review Summary: ✅ Completed

This comment shows the latest Codex review activity on this pull request.

Review Status Commit Review trigger
📝 Code Review ✅ Completed 2026-11-09T20:13:07.922378Z 88bc236 Draft marked ready
🔒 Security Review ✅ Completed 2026-11-09T20:13:41.849849Z 88bc236 Draft marked ready
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@mz1119
Merge remote-tracking branch 'origin/main' into max.zhang/mcp-client-…
9f4ce67 
…info

# Conflicts:
#	contrib/mark3labs/mcp-go/tracing.go
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