Conciseness

The body is lean and dense with non-obvious repository-specific knowledge ('`asyncio_mode = "auto"` is configured globally', '`pythonpath` in pyproject shadows `PYTHONPATH`', 'The default timeout is five seconds') and never explains concepts Claude already knows. Every token earns its place, matching anchor 5.

Actionability

Concrete, executable guidance is given throughout ('Use `Client(server)` for real MCP dispatch', 'capture the outgoing request with `httpx2.MockTransport`', 'pin `mode="legacy"` only when the handshake era is the subject', 'copy it into a main worktree'). It falls short of anchor 5 because there is no copy-paste-ready example test covering the common cases, though it is well above anchor 3's pseudocode level.

Workflow Clarity

A clear sequence with explicit validation checkpoints is present ('Read nearby tests ... first', 'run the regression against unchanged code and confirm it fails for the reported reason, then run it with the fix', 'Run focused tests during development, then the full commands required by AGENTS.md before committing'), including error-recovery guidance ('If a failure appears unrelated, reproduce it on the unchanged base'). It misses anchor 5 because the sequence is dispersed across prose and bullets rather than presented as explicit ordered steps with a checklist.

Progressive Disclosure

The skill is a 21-line body with no bundle files, well organized into a heading, orientation paragraph, and focused bullets, and its single reference (the '[testing guide](../../../docs/development/tests.mdx)') is clearly signaled and one level deep. Per the rubric guideline for skills under 50 lines with no need for external references, this matches anchor 5.

Specificity

The description names the domain ('regression tests for FastMCP changes') and one concrete action with specific instruments ('using its pytest fixtures, in-memory clients, and protocol boundaries'), but lists only a single action rather than several, matching anchor 3. It is well above anchor 2 ('names the domain but actions are minimal') yet does not list several distinct actions as anchor 4 requires.

Completeness

The 'what' is clear ('Write regression tests for FastMCP changes using its pytest fixtures, in-memory clients, and protocol boundaries') but there is no 'Use when...' clause or equivalent explicit trigger guidance, capping completeness at 3 per the rubric guidelines. It is far above anchor 2, which requires a vague 'what' or no 'what' at all.

Trigger Term Quality

Natural domain keywords are present ('regression tests', 'pytest', 'FastMCP', 'in-memory clients') that a user would genuinely say, matching anchor 4's 'good keyword coverage; a few natural terms missing'. It falls short of anchor 5 because common variations like 'testing', 'unit tests', or 'test suite' are absent.

Distinctiveness Conflict Risk

The combination of 'FastMCP', 'regression tests', and 'pytest fixtures' establishes a clear niche with distinct triggers and minimal conflict risk, matching anchor 5. Even a general Python-testing skill would not be wrongly triggered by this description.