Conciseness

The body is lean and assumes Claude's competence: it never explains what an API key or environment variable is, and every line is either ToolUniverse-specific data (setting names, URLs, approval waits) or behavioral guidance ("explain in plain words, one step at a time"). Even seemingly small lines earn their place (e.g., "If the key arrives by email, the user opens it themselves" reinforces the security rule), matching the every-token-earns-its-place anchor rather than the level-4 'minor trimming' anchor.

Actionability

For an instruction-only skill the guidance is fully concrete: a table with exact setting names (`NCBI_API_KEY`, `OMIM_API_KEY`, ...), provider URLs for obtaining each key, exact hosted steps (open the credentials URL, search, paste, **Save key**), local steps with the exact env-var name and where to set it, and a concrete verification example ("a well-known gene such as `BRCA1`"). It covers the common cases (hosted and local) like the copy-paste-ready anchor requires.

Workflow Clarity

The four numbered sections give a clear sequence (find login → get key → save it → check it works) with an explicit validation step that enumerates outcome branches and remediation: "Still 'missing'... Check the exact name", "'Rejected'... typo, not activated yet, or the account lacks API access", "A different error... it is not the login". This is exactly the explicit-validation-with-error-recovery pattern of the level-5 anchor; the operation is non-destructive so no cap applies.

Progressive Disclosure

There are no bundle files (references/, scripts/, assets/ are absent), and the skill needs none: it is a compact ~40 content-line, single-file skill with well-organized sections (## 1–## 4), a scannable lookup table, and an appropriate external pointer for the long tail ("The full list, with steps for each, is on https://connect.aiscientist.tools/credentials"). This fits the small-skill exception: well-organized sections with no nested or buried references.

Specificity

The description lists multiple concrete actions — "Explains which login unlocks what, where to get it, where to paste it, and retries the tool" — plus the distinctive constraint "without the key ever passing through the chat", covering the whole workflow comprehensively. It goes beyond the level-4 anchor ("several specific actions; minor gaps") because no part of the task workflow is left unspecified, and the voice is imperative/third person ("Help the user add..."), so no person-penalty applies.

Completeness

Both questions are answered explicitly: what ("add the login (API key)... Explains which login unlocks what, where to get it, where to paste it, and retries the tool") and when ("Use when a tool says a login, API key or token is missing or rejected, or the user asks...") with concrete trigger phrases. This mirrors the level-5 example structure of explicit what + explicit Use-when with quoted triggers, and the 'Use when' clause is present so no cap applies.

Trigger Term Quality

Natural trigger coverage is comprehensive: synonyms "login, API key or token", concrete database names (NCBI/PubMed, OMIM, DisGeNET, UMLS, OpenAlex), and quoted user phrasings like "add my OMIM key" and "why does this database need a key". These are exactly the phrases a user would say; nothing common is missing, matching the comprehensive-synonyms anchor.

Distinctiveness Conflict Risk

The niche is precise — ToolUniverse database logins with named settings like `OMIM_API_KEY`-style errors and specific databases — so it would not plausibly trigger for unrelated skills. Triggers ("login, API key or token is missing or rejected") combined with the ToolUniverse framing give it minimal conflict risk, matching the clear-niche anchor.