Conciseness

The body is lean with no explanation of concepts Claude already knows, and sections like Package Facts and Guardrails carry genuinely non-obvious, project-specific information. It sits at anchor 4 rather than 5 because the "When To Use" bullet list and intro largely restate the frontmatter description, which is already loaded with the skill and could be trimmed.

Actionability

The Core Pattern is real Go ("pb := ax.Playbook(program, ...)"; "pb.Evolve(ctx, examples, metricFn, nil)") but relies on undefined surrounding variables (llm, examples, metricFn), so it is a shape sketch rather than executable code. More importantly, the Core Pattern uses the `ax.` prefix while "Relevant API Surface" lists the same functionality as `axllm.Playbook`/`axllm.Optimize`, a concrete contradiction an agent could copy incorrectly — matching the anchor for concrete guidance with missing key details.

Workflow Clarity

A rough sequence is implied by the "When To Use" bullets (grow playbook → attach and learn from run-end signals → evolve → refine → render) plus the Core Pattern, but steps are not explicitly sequenced and validation checkpoints are absent — only the guardrail "Start from package examples for exact native syntax" serves as an implicit check. This matches the anchor for steps listed with missing or implicit checkpoints; it exceeds anchor 2 because a genuine sequence is discernible.

Progressive Disclosure

The body is under 50 lines, has no bundle files, and is organized into clear well-labeled sections (When To Use, Package Facts, Core Pattern, Relevant API Surface, Guardrails). Pointers to package-side detail (API.md, axir-api.json, examples/) are one level deep and clearly named, satisfying the simple-skill case for a top score.

Specificity

The description lists several concrete capabilities — "playbook() context-engineering surface, agent-bound verified evolution, run-end learning, online updates, and rendering a playbook into a program" — which matches the anchor for several specific actions with minor gaps. It falls short of the comprehensive anchor (5) because the actions are phrased in dense internal jargon rather than fully concrete terms, and above anchor 3 because more than 1-2 actions are named.

Completeness

An explicit "Use when..." trigger clause is present ("Use when writing Go code with `github.com/ax-llm/ax/packages/go` for..."), and the "what" is conveyed through the enumerated capability list. It matches anchor 4 — both what and when are present, but the "what" is folded into the when-clause and delivered in jargon rather than clearly and separately stated as the anchor-5 example does.

Trigger Term Quality

It includes natural terms a user of this package would actually say — "writing Go code", "playbook", the package import path "github.com/ax-llm/ax/packages/go" — giving good keyword coverage. It is below the comprehensive anchor (5) because synonyms and common variations (e.g., "ax", "context engineering", "optimize") are only partially covered.

Distinctiveness Conflict Risk

The description pins a specific package import path and a named API surface ("playbook()", "agent-bound verified evolution", "run-end learning") that belong to a clear niche, so it would rarely trigger for the wrong skill. This clearly matches the anchor for a clear niche with distinct triggers and minimal conflict risk.