Conciseness

The body is dominated by executable commands and lookup tables with little concept explanation, matching the 'efficient; minor instances of over-explanation that could be trimmed' anchor. It falls short of lean-per-token because the dataset provenance is repeated ('sourced from YC's Algolia search index and updated daily' in the intro, refreshed-daily again in Step 4), and the host-specific shell-probe note about 'if your host has not already executed the commands... (for example, in Codex)' is environment noise rather than task content.

Actionability

Everything needed to execute is concrete and copy-paste ready: the base URL, complete curl|jq one-liners ('curl -s https://yc-oss.github.io/api/companies/top.json | jq .'), a routing table from user intent to endpoint, a jq filter cookbook, and discovery commands against meta.json. This matches the 'fully executable; specific examples cover the common cases' anchor, not the level below with minor gaps.

Workflow Clarity

Five clearly sequenced steps with explicit validation (the prerequisite probe reporting CURL_OK/JQ_OK) and a genuine feedback loop in Step 5 (error → cause → fix table: 404 → check meta.json; empty array → broaden the search). As a read-only skill there are no destructive/batch operations, so the validation cap does not apply; this fits the 'explicit validation steps; feedback loops for error recovery' anchor better than level 4's 'minor validation gaps'.

Progressive Disclosure

The SKILL.md body is a concise overview (routing table, base pattern, key rules) with a single, clearly signaled, one-level-deep reference — references/api_reference.md exists and contains the field schema, full endpoint list, and research workflow examples without nesting further files. The inline 'when to read it' guidance ('when you need the exact company field schema, valid batch/industry/tag names...') matches the 'clear overview with well-signaled one-level-deep references' anchor; it exceeds level 4 because there is no mislaid content or unclear signaling.

Specificity

The description enumerates concrete, distinct capabilities — 'company profiles, batch rosters (e.g. W25, S24), companies by industry or tag, top companies, who is hiring, founder-diversity lists, and overall YC stats' — grounded in a named mechanism (the public yc-oss static JSON API). This matches the 'multiple specific concrete actions; comprehensive coverage' anchor, not the level below where minor gaps remain.

Completeness

It explicitly answers 'what' (the capability list plus the data source and refresh cadence) and 'when' via a concrete 'Use this skill whenever the user asks about...' clause enumerating trigger scenarios. This is the anchor-5 pattern of a clear what paired with an explicit when; it exceeds the level-4 anchor where the 'when' is less specific.

Trigger Term Quality

Triggers include natural phrasings users would actually say — 'YC-backed startups', 'a YC batch', 'YC companies in a sector or tag or that are hiring', 'the Y Combinator portfolio', 'startup and venture research' — with synonyms covered (both 'YC' and 'Y Combinator', plus batch short forms W25/S24). Coverage is comprehensive rather than the 'a few natural terms missing' level.

Distinctiveness Conflict Risk

The niche is narrowly bounded to YC-sourced data, and triggers like 'YC batch', 'YC-backed startups', and 'the Y Combinator portfolio' would not plausibly fire a different skill; the 'startup and venture research that draws on YC data' qualifier further bounds the broadest trigger. Clear niche with distinct triggers, minimal conflict risk.