Lean and efficient: the 'When to use' paragraph explains non-obvious Pi registry mechanics rather than concepts Claude already knows, and the JSON block is necessary and copy-ready, so every token earns its place.

Provides concrete file paths, a complete copy-ready models.json example, and specific verification commands ('pi --list-models | grep <id>' and a smoke-test invocation), all directly executable.

Five clearly sequenced steps with pre-flight validation checkpoints (confirm slug is real, confirm auth) and an explicit verify step (step 5) including JSON-parse and model-list checks.

A single-purpose skill under 50 lines with no bundle files, organized into clear sections (When to use, Files, Steps, Quirks); per the simple-skills note this qualifies for a top score.

It names a concrete action ('Register a custom or variant model … so it can be set as the global default') with variant examples, but centers on a single action rather than listing multiple concrete actions, matching anchor 2 rather than 3.

Clearly answers both what ('Register a custom or variant model … as the global default') and when ('Use when Pi silently falls back … or when a model slug isn't in Pi's bundled list') with explicit triggers.

Explicit 'Triggers on' natural user phrases ('Pi reset my model', 'Pi won't use this model', 'add a model to Pi', 'Pi default keeps reverting') give good coverage of terms users would actually say.

Highly niche scope (Pi Agent, OpenRouter variant slugs, a specific fallback model) gives it a clear niche unlikely to trigger for unrelated skills.