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All skill reviews
Every skill below was run on a standard task with and without it loaded, scored on our published 100-point rubric, and screened against six security red lines. Sorted by score — the evidence is on each page.
xlsx
Anthropic's spreadsheet skill: live formulas only, a professional formatting standard, and a mandatory LibreOffice recalculation pass before any workbook ships.
“The first skill in our tests whose edge over the baseline is binary rather than a matter of taste: identical formula logic on both sides, but only the with-skill workbook shipped values a reader could actually see, because the skill mandates the recalculation pass nobody runs unprompted. Caveats: it needs LibreOffice installed, and the licence is proprietary.”
Read the full review →writing-plans
The Superpowers planning skill: turns a spec into a bite-sized, TDD-shaped implementation plan — exact files, exact signatures, a failing test before every implementation step.
“The strongest workflow skill we have tested. Its plan is executable by a developer who has never seen the codebase — 26 checkbox steps, 14 tests written as code, exact signatures in every task — where a competent baseline outline still leaves every interface to be invented. Docked for a description with no off-switch and a plan header that hard-wires Superpowers' own execution skills.”
Read the full review →Anthropic's PDF cookbook: working recipes for extraction, merging, splitting, watermarks, encryption, OCR and form filling, plus eight helper scripts.
“On clean PDFs it ties with doing it yourself — the score comes from everything around that: twenty recipes that run as written, a proper form-filling validation loop, and the best file layering we have tested. Two honest caveats: it is proprietary-licensed, and it triggers on any PDF mention.”
Read the full review →semgrep
Trail of Bits' approval-gated Semgrep scan: language detection, ruleset selection, a hard plan-approval step, parallel scans and merged SARIF — with telemetry off by construction.
“The strongest process we have scored — hard approval gate, failure accounting, telemetry off by construction — wrapped around a scanner that missed the SQL injection in a 71-line file. Trust it to run a scan honestly; do not trust the scan alone to clear a file.”
Read the full review →frontend-design
Anthropic's official skill for distinctive, non-templated visual design — aesthetic direction, typography and layout guidance for new UI.
“The rare guidance skill whose live output is visibly less generic than baseline — docked mainly for a vague trigger description and zero worked examples.”
Read the full review →github-actions-efficiency
GitHub's CI cost-cutting playbook from the awesome-copilot collection: audit a workflow's waste in a fixed order, apply guarded fixes — caching, stale-run cancellation, trigger scoping — and report savings without inventing them.
“A disciplined audit playbook whose guardrails and honesty rules are the best we have scored — held back by a description that hides its creation mode, a cache pattern one idiom behind the baseline, and a test workflow that differed from no-skill output in exactly one block: it cancelled stale runs.”
Read the full review →webapp-testing
Anthropic's Playwright toolkit for testing local web apps: a reconnaissance-then-action pattern, a server-lifecycle helper script, and three worked examples.
“A sound browser-driving method wrapped around one useful script — reconnaissance before action, selectors from the rendered page, servers managed for you. It teaches an agent to operate a web app, not to judge one: there is no assertion guidance anywhere in its 95 lines, and its own server helper caused the only crash in our test run.”
Read the full review →brand-guidelines
Anthropic's official brand card: seven exact colours and two font stacks for styling artifacts with Anthropic's look-and-feel.
“Seventy-three lines of exact, copy-paste brand data that measurably beat a strong baseline on fidelity — 7 of 7 colours exact, both fonts right. But it is a data card, not a workflow: no steps, no checks, a trigger that can fire on other companies' brands, and feature text describing a PowerPoint script that does not ship.”
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