Conciseness

The body is mostly dense and efficient — tables, checklists, and executable code with little concept re-teaching. A few padded spots could be trimmed ("Build SDKs that developers can't stop talking about. Great SDK DX is a competitive advantage…", "SDK documentation has three layers: all three are needed", and the translated-JavaScript-SDK sentence that repeats a reference file's opening), so it fits anchor 4 rather than 5.

Actionability

Guidance is copy-paste ready throughout: a complete tsup.config.ts, a full package.json exports block, an error-class hierarchy with required fields, a JSDoc template, a doc-generator table per language, and phase gates citing concrete tools (publint, attw, npm publish --dry-run). Specific examples cover the common cases, matching anchor 5.

Workflow Clarity

The four-phase lifecycle is clearly sequenced (Design → Build → Document → Ship table, "State which phase you're in… the skill routes accordingly") with an explicit "Phase gates" section of verification questions between phases, a pre-release quality checklist, and a closing "Did this help?" feedback loop with an issue-filing path. This matches anchor 5: clear sequence, explicit validation checkpoints, and checklists.

Progressive Disclosure

All four bundle files (references/design-principles.md, language-idioms.md, typescript-sdk.md, build-and-publish.md) exist, are referenced one level deep, and are clearly signaled via blockquotes at the point of need in the matching phase sections. The overview inlines only summaries and examples, matching the anchor-5 split pattern; the only nit is the body's "§ Type Safety" label versus the actual "Type safety patterns" heading, which is too minor to drop the score.

Specificity

The description names the domain and four concrete lifecycle actions ("Design, build, document, and ship SDKs") plus concrete contexts ("creating a client library, planning a breaking change, or reviewing SDK quality"). It stops short of anchor 5 because coverage has minor gaps — no mention of languages, publishing targets, or versioning specifics.

Completeness

It explicitly answers both questions: the what is "Design, build, document, and ship SDKs" and the when is "Use when creating a client library, planning a breaking change, or reviewing SDK quality" with concrete trigger phrases, matching the anchor-5 example structure. It does not fall to 4 because the when-clause is explicit and specific, not merely present.

Trigger Term Quality

Natural phrases a user would say are present: "SDKs", "client library", "breaking change", "SDK quality", plus boundary terms "CLI" and "MCP server". A few natural variations are missing (e.g., "npm package", "API wrapper", "publish"), so it fits anchor 4 rather than 5.

Distinctiveness Conflict Risk

The explicit negative boundary ("It does not build a CLI (that's `devrel-tooling`) or an MCP server (that's `mcp-server-craft`)") carves out a clear niche and redirects near-miss triggers to sibling skills, giving minimal conflict risk — a direct match for anchor 5.