Add annotation cache for tools/list to tools/call flow#4114
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## main #4114 +/- ##
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- Coverage 68.84% 68.83% -0.02%
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Files 458 459 +1
Lines 46274 46319 +45
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+ Hits 31859 31884 +25
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The authz middleware now caches tool annotations from tools/list responses and injects them into context during tools/call requests. This bridges the gap where annotations are visible in tools/list but lost by the time tools/call arrives as a separate HTTP request. - Add AnnotationCache with concurrent-safe get/set operations - ResponseFilteringWriter populates cache during tools/list filtering - Middleware closure captures cache, injects annotations for tools/call - Graceful degradation when tools/call arrives before tools/list Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
SetFromToolsList previously merged into the existing map, so tools whose annotations were removed in a subsequent tools/list response retained stale cached entries. Replace the entire map atomically to ensure eviction of removed tools. Also add a test for the eviction behavior and document the intentional omission of the Title field in convertMCPAnnotation. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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JAORMX
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Mar 12, 2026
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JAORMX
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Thanks for the review! Replied inline.
jhrozek
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Mar 12, 2026
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jhrozek
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lgtm, two questions inline, not acking because Alejandro had another comment
aponcedeleonch
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Mar 12, 2026
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aponcedeleonch
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lgtm, Jakub had a comment about pagination that could be potentially worth looking into (?) as he mentioned, I don't know how real-world issue pagination is
jhrozek
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Mar 12, 2026
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Summary
tools/listresponses but lost by the timetools/callarrives as a separate HTTP request. This adds an in-memory annotation cache that bridges the two operations, enabling Cedar/HTTP PDP policies to reference annotations duringtools/callauthorization.Type of change
Test plan
task test)task lint-fix)Changes
pkg/authz/annotation_cache.goAnnotationCachewith concurrent-safeGet/Set/SetFromToolsList, nil-safe on nil receiverpkg/authz/annotation_cache_test.gopkg/authz/response_filter.goResponseFilteringWritergainsannotationCachefield;filterToolsResponsepopulates cache from parsed tool listpkg/authz/middleware.goMiddlewareclosure creates per-proxy cache;tools/calllooks up annotations and injects viaWithToolAnnotationspkg/authz/response_filter_test.goNewResponseFilteringWritercall sites for new parameterDoes this introduce a user-facing change?
No — internal plumbing. Users benefit when Cedar policies reference tool annotations (e.g.
resource.readOnlyHint == true), which now work fortools/callafter atools/listhas populated the cache.Special notes for reviewers
Middlewareclosure, so each MCP server proxy has its own cache. Tool names are scoped to a single server, so this is correct.tools/callarrives before anytools/list,Getreturns nil and no annotations are injected — same behavior as before PR 1.AnnotationCachemethods handle nil receiver, so existing code passingniltoNewResponseFilteringWriterworks unchanged.SetFromToolsListruns before the authorization loop, so annotations for all tools (including ones that will be filtered out) are cached.Generated with Claude Code