nix-best-practices

Nix patterns for flakes, overlays, unfree handling, and binary overlays. Use when working with flake.nix or shell.nix.

1.59x

Quality

—

Does it follow best practices?

Impact

91%

1.59x

Average score across 3 eval scenarios

Securityby

Passed

No known issues

Quality

Content

80%

Reviews the quality of instructions and guidance provided to agents. Good implementation is clear, handles edge cases, and produces reliable results.

A code-dense, highly actionable Nix reference with minimal fluff and good section organization. It loses points only on workflow sequencing (no explicit validation checkpoints) and progressive disclosure (a monolithic single file where the large binary-overlay pattern could be split out).

Suggestions

Add explicit validation checkpoints to multi-step processes, e.g. after fetching a SHA256 hash, add 'verify with nix hash to-sri before pasting into flake.nix; if nix build reports a hash mismatch, re-fetch and retry'.

Extract the large binary-overlay-repo pattern into a references/ file (e.g. BINARY_OVERLAY.md) and link to it from SKILL.md so the main file stays a lean overview.

Turn the binary-overlay creation flow into a numbered sequence (write flake.nix → prefetch hashes → convert to SRI → build with nix build .#tool → verify) with a checkpoint after each step.

Dimension	Reasoning	Score
Conciseness	The body is overwhelmingly executable Nix code with minimal prose, assumes Claude's competence with Nix, and avoids explaining concepts Claude already knows, matching the 'lean and efficient' level-3 anchor.	3 / 3
Actionability	It provides complete, copy-paste-ready flake.nix examples, specific commands (nix-prefetch-url, nix hash to-sri, nix flake check), and concrete overlay/unfree patterns, meeting the level-3 'fully executable, copy-paste ready' bar.	3 / 3
Workflow Clarity	Topics are organized as standalone pattern sections rather than numbered multi-step sequences with validation checkpoints; e.g., binary-overlay creation and hash fetching have an implicit order but no explicit validate-then-proceed feedback loop, fitting the level-2 anchor.	2 / 3
Progressive Disclosure	Everything lives in a single ~350-line SKILL.md with no bundle files, and the large binary-overlay section (~75 lines) is content that could plausibly be a separate reference, matching the level-2 'content that should be separate is inline' anchor despite clear section headers.	2 / 3
	Total	10 / 12 Passed

Description

90%

Based on the skill's description, can an agent find and select it at the right time? Clear, specific descriptions lead to better discovery.

A strong, third-person description that clearly states both capability and trigger conditions with natural Nix vocabulary. Its only weakness is framing capabilities as 'patterns for' rather than enumerating concrete actions.

Dimension	Reasoning	Score
Specificity	The description names the Nix domain and four concrete subtopics ("flakes, overlays, unfree handling, and binary overlays") but frames them as "patterns for" rather than listing concrete actions like the top anchor's 'extract, fill, merge', so it stops short of the level-3 action list.	2 / 3
Completeness	It states what the skill covers ("Nix patterns for flakes, overlays, unfree handling, and binary overlays") and gives an explicit when trigger ("Use when working with flake.nix or shell.nix"), satisfying both halves required for a 3.	3 / 3
Trigger Term Quality	It uses natural terms a Nix user would actually say — "flake.nix", "shell.nix", "flakes", "overlays", "unfree" — giving good coverage of the domain's common vocabulary, matching the level-3 anchor.	3 / 3
Distinctiveness Conflict Risk	The Nix/flake-specific triggers (flake.nix, shell.nix) carve out a clear niche unlikely to fire for unrelated skills, matching the level-3 'clear niche with distinct triggers' anchor.	3 / 3
	Total	11 / 12 Passed

Validation

100%

Warnings & errors only

Checks the skill against the spec for correct structure and formatting. All validation checks must pass before discovery and implementation can be scored.

Validation — 16 / 16 Passed

Validation for skill structure

No warnings or errors.

Repository: NeverSight/skills_feed
Commit: c2b0563

Reviewed: 5 days ago

Table of Contents

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