The body is code-heavy and lean — actionable prose like 'Always close' and 'Use payload' earns its place, with only minor restatements ('Per the README's quickstart pattern... The test pattern is inject then close') that don't rise to the level-2 'Mostly efficient but includes some unnecessary explanation'.

It provides fully executable, copy-paste-ready code (buildApp, app.inject, validationRules, depth-limit test) plus a concrete anti-pattern table with explicit fixes, matching the 'Fully executable code/commands; copy-paste ready' anchor rather than level 2's 'pseudocode instead of executable code'.

The testing workflow is clearly sequenced (build → register → inject → assert → close) with beforeEach/afterEach lifecycle, and the expect() assertions act as explicit validation checkpoints, hitting the 'Clear sequence with explicit validation steps' anchor rather than level 2's 'checkpoints missing or implicit'.

With no bundle files present, the body is organized into clear sections (Overview → Authoring → Running → Parsing → CI → Anti-patterns → Limitations → References) with well-signaled one-level-deep external URLs and companion-skill pointers, matching the 'Clear overview with well-signaled one-level-deep references' anchor.

Lists multiple concrete actions — 'app.inject() for HTTP-layer simulation', 'plugin-registration setup', 'production-config gates (graphiql: false; jit threshold; query depth limits)', and 'per-test app lifecycle (app.close() in afterEach)' — in third person ('Wraps...'), matching the 'Lists multiple specific concrete actions' anchor rather than the level-2 'Names domain and some actions'.

It explicitly answers both what (the four testing-pattern groups) and when via a clear 'Use when...' trigger, hitting the 'Clearly answers both what AND when' anchor instead of level 2 where 'when is missing or only implied'.

The 'Use when writing tests for a Fastify + Mercurius GraphQL server' clause surfaces natural terms ('tests', 'Fastify', 'Mercurius', 'GraphQL server') a developer would actually say, giving good coverage rather than the level-2 'Some relevant keywords but missing common variations'.

The narrow Mercurius + Fastify GraphQL testing niche (with sibling frameworks distinguished in the body) gives a clear, distinct trigger unlikely to fire for the wrong skill, matching the 'Clear niche with distinct triggers' anchor.