Nodejs Backend Patterns
ever-works/ever-works
Build production-ready Node.js backend services with Express/Fastify, implementing middleware patterns, error handling, authentication, database integration, and API design best practices.
Validate API changes against an expected contract. An agent skill from proflead/codex-skills-library.
Install API Contract Checker
$ npx skills add proflead/codex-skills-library --skill api-contract-checker -a claude-codeProject install by default; add -g for ~/.claude/skills/.
$ gh skill install proflead/codex-skills-library api-contract-checker --agent claude-codeProject scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).
$ git clone --depth 1 https://github.com/proflead/codex-skills-library.git skills-src && mkdir -p .claude/skills && cp -r skills-src/skills/api/api-contract-checker .claude/skills/api-contract-checker && rm -rf skills-srcUse ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.
Claude Code skills documentation · loads skills from .claude/skills/
Install the "api-contract-checker" agent skill from https://github.com/proflead/codex-skills-library/tree/master/skills/api/api-contract-checker into .claude/skills/api-contract-checker/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "api-contract-checker", then confirm the skill loads.Claude Code copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$skill-installer install https://github.com/proflead/codex-skills-library/tree/master/skills/api/api-contract-checkerType this inside Codex. $skill-installer <name> installs a curated skill from openai/skills. The installer writes to $CODEX_HOME/skills (default ~/.codex/skills). Restart Codex if the skill does not show up.
$ npx skills add proflead/codex-skills-library --skill api-contract-checker -a codexProject install goes to .agents/skills/; add -g for ~/.codex/skills/.
$ gh skill install proflead/codex-skills-library api-contract-checker --agent codexProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/proflead/codex-skills-library.git skills-src && mkdir -p .agents/skills && cp -r skills-src/skills/api/api-contract-checker .agents/skills/api-contract-checker && rm -rf skills-srcUse ~/.agents/skills/ instead of .agents/skills for a personal install.
Codex skills documentation · loads skills from .agents/skills/
Install the "api-contract-checker" agent skill from https://github.com/proflead/codex-skills-library/tree/master/skills/api/api-contract-checker into .agents/skills/api-contract-checker/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "api-contract-checker", then confirm the skill loads.Codex copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ npx skills add proflead/codex-skills-library --skill api-contract-checker -a cursorProject install goes to .agents/skills/; add -g for ~/.cursor/skills/.
$ gh skill install proflead/codex-skills-library api-contract-checker --agent cursorProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/proflead/codex-skills-library.git skills-src && mkdir -p .cursor/skills && cp -r skills-src/skills/api/api-contract-checker .cursor/skills/api-contract-checker && rm -rf skills-srcUse ~/.cursor/skills/ instead of .cursor/skills for a personal install.
Cursor skills documentation · loads skills from .cursor/skills/, .agents/skills/, .claude/skills/, .codex/skills/
Install the "api-contract-checker" agent skill from https://github.com/proflead/codex-skills-library/tree/master/skills/api/api-contract-checker into .cursor/skills/api-contract-checker/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "api-contract-checker", then confirm the skill loads.Cursor copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ gemini skills install https://github.com/proflead/codex-skills-library.git --path skills/api/api-contract-checker--scope user (default) or --scope workspace; --path is the subfolder of the repo that holds the skill; --consent skips the security confirmation prompt.
$ npx skills add proflead/codex-skills-library --skill api-contract-checker -a gemini-cliProject install goes to .agents/skills/; add -g for ~/.gemini/skills/.
$ gh skill install proflead/codex-skills-library api-contract-checker --agent gemini-cliProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/proflead/codex-skills-library.git skills-src && mkdir -p .gemini/skills && cp -r skills-src/skills/api/api-contract-checker .gemini/skills/api-contract-checker && rm -rf skills-srcUse ~/.gemini/skills/ instead of .gemini/skills for a personal install, then run /skills reload.
Gemini CLI skills documentation · loads skills from .gemini/skills/, .agents/skills/
Install the "api-contract-checker" agent skill from https://github.com/proflead/codex-skills-library/tree/master/skills/api/api-contract-checker into .gemini/skills/api-contract-checker/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "api-contract-checker", then confirm the skill loads.Gemini CLI copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ gh skill install proflead/codex-skills-library api-contract-checkerInstalls for Copilot at project scope by default; add --scope user for a personal install. Preview a skill first with gh skill preview. Needs GitHub CLI 2.90.0 or later (public preview).
$ npx skills add proflead/codex-skills-library --skill api-contract-checker -a github-copilotProject install goes to .agents/skills/; add -g for ~/.copilot/skills/.
$ git clone --depth 1 https://github.com/proflead/codex-skills-library.git skills-src && mkdir -p .github/skills && cp -r skills-src/skills/api/api-contract-checker .github/skills/api-contract-checker && rm -rf skills-srcUse ~/.copilot/skills/ instead of .github/skills for a personal install. Commit .github/skills so cloud agent and code review can use it.
GitHub Copilot skills documentation · loads skills from .github/skills/, .claude/skills/, .agents/skills/
Install the "api-contract-checker" agent skill from https://github.com/proflead/codex-skills-library/tree/master/skills/api/api-contract-checker into .github/skills/api-contract-checker/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "api-contract-checker", then confirm the skill loads.GitHub Copilot copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ npx skills add proflead/codex-skills-library --skill api-contract-checker -a opencodeOpenCode documents no install command of its own. Project install goes to .agents/skills/; add -g for ~/.config/opencode/skills/.
$ gh skill install proflead/codex-skills-library api-contract-checker --agent opencodeProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/proflead/codex-skills-library.git skills-src && mkdir -p .opencode/skills && cp -r skills-src/skills/api/api-contract-checker .opencode/skills/api-contract-checker && rm -rf skills-srcUse ~/.config/opencode/skills/ instead of .opencode/skills for a personal install.
OpenCode skills documentation · loads skills from .opencode/skills/, .claude/skills/, .agents/skills/
Install the "api-contract-checker" agent skill from https://github.com/proflead/codex-skills-library/tree/master/skills/api/api-contract-checker into .opencode/skills/api-contract-checker/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "api-contract-checker", then confirm the skill loads.OpenCode copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
Facts
- Skill name
api-contract-checker- GitHub stars
- 155
- Token cost
- ~185 tokens
- SKILL.md length
- 74 words
- Files
- 1
- Skills in repo
- 10
- Repo updated
- First seen
- Licence
- None found
At a glance
Validate API changes against an expected contract. An agent skill from proflead/codex-skills-library.
- Works in 3 steps: Compare endpoints, request/response… → Identify breaking changes and… → Suggest versioning or migration notes.
- A mid-level developer needs to detect breaking changes
- SKILL.md covers Purpose, Inputs to request, Workflow and Output, plus 1 more section
- Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md
What it does
API Contract Checker is an agent skill from proflead/codex-skills-library. Validate API changes against an expected contract. Use when a mid-level developer needs to detect breaking changes.
Its SKILL.md is about 190 tokens, which your agent loads only when the skill is triggered. It is a single SKILL.md file with no bundled scripts.
It sits in Backend & APIs, covering API design. The repository describes itself as: Codex Skills Library is a curated library of reusable Codex skills for developers, individuals, and teams.
When your agent uses it
- A mid-level developer needs to detect breaking changes
- Tasks that involve API design
Example prompts
- “/api-contract-checker”
Workflow steps
3 steps, taken from the first numbered list in SKILL.md.
- Compare endpoints, request/response fields, and status codes.
- Identify breaking changes and backward-compatible adjustments.
- Suggest versioning or migration notes.
What it can do on your machine
Read from SKILL.md and the folder at commit a05260c. It shows what the files ask for, not the result of running them.
Tool permissions
Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.
From allowed-tools in the SKILL.md frontmatter.
Runs code
No scripts in the folder and no shell commands in SKILL.md.
From the folder's file list and the shell code blocks in SKILL.md.
Network
No URLs in SKILL.md.
From URLs in SKILL.md, links to its own repository left out.
Credentials
Names no API keys, tokens, secrets or passwords.
From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.
Context cost
API Contract Checker loads about 185 tokens when it runs. Until then it costs about 34 tokens; SKILL.md has 74 words of instructions outside code blocks.
Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.
Safety
Auto-check passed
The automated check found no risky patterns in SKILL.md.
Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.
SKILL.md
Without a licence we can't republish the file, so here is its outline and opening line. It has 74 words (~185 tokens).
“Validate API changes against an expected contract.”
- name
- api-contract-checker
Files
Just SKILL.md in skills/api/api-contract-checker of proflead/codex-skills-library.
Open the folder on GitHubat commit a05260c
Compare with similar skills
API Contract Checker next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.
| Skill | Stars | Used in | Tokens | Auto-check | Licence | Repo updated |
|---|---|---|---|---|---|---|
| API Contract Checker this skillproflead/codex-skills-library | 155 | — | ~185 | Automated safety check: Pass | None | |
| Nodejs Backend Patternsever-works/ever-works | 162 | 18 repos | ~4k | Automated safety check: Pass | AGPL-3.0 | |
| API DesignerJeffallan/claude-skills | 12k | 1 repos | ~2k | Automated safety check: Pass | MIT | |
| Pangolin CRUD Endpointsfosrl/pangolin | 23k | — | ~461 | Automated safety check: Pass | Custom licence | |
| Backend PatternshellangleZ/burn-in-cceverywhere-ralph | 112 | 17 repos | ~3.3k | Automated safety check: Pass | None | |
| API Design Principlesjh941213/my-cc-harness | 125 | 18 repos | ~3.4k | Automated safety check: Pass | None |
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API Designer
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Pangolin CRUD Endpoints
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Use whenever asked to add, create, or scaffold a CRUD endpoint, router, or entity in this repo's server (create/list/get/update/delete handlers, new…
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Backend architecture patterns, API design, database optimization, and server-side best practices for Node.js, Express, and Next.js API routes.
API Design Principles
jh941213/my-cc-harness
REST 및 GraphQL API 설계 원칙 가이드. An agent skill from jh941213/my-cc-harness.
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Categories
Questions about API Contract Checker
What does API Contract Checker do?
Validate API changes against an expected contract. An agent skill from proflead/codex-skills-library. API Contract Checker is an agent skill from proflead/codex-skills-library. Validate API changes against an expected contract.
When should I use API Contract Checker?
API Contract Checker fits situations like: A mid-level developer needs to detect breaking changes; tasks that involve API design.
How do I install API Contract Checker in Claude Code?
Run `npx skills add proflead/codex-skills-library --skill api-contract-checker -a claude-code`. Or copy the skill folder (skills/api/api-contract-checker in proflead/codex-skills-library) into .claude/skills/api-contract-checker in your project. Claude Code loads it when a task matches its description.
How do I install API Contract Checker in Codex?
Run `npx skills add proflead/codex-skills-library --skill api-contract-checker -a codex`. Or copy the skill folder (skills/api/api-contract-checker in proflead/codex-skills-library) into .agents/skills/api-contract-checker in your project. Codex loads it when a task matches its description.
Can I use API Contract Checker in Cursor, Gemini CLI or GitHub Copilot?
Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add proflead/codex-skills-library --skill api-contract-checker -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/api-contract-checker, .gemini/skills/api-contract-checker, .github/skills/api-contract-checker and .opencode/skills/api-contract-checker in your project.
What does API Contract Checker need to run?
SKILL.md names no scripts, command-line tools or credentials: API Contract Checker is instructions for the agent only.
Does API Contract Checker access the network?
SKILL.md contains no URLs. Any network use would come from the scripts or tools the agent runs. This is read from the text; nothing was executed.
Is API Contract Checker safe to install?
Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.
What licence does API Contract Checker use?
No licence was found for API Contract Checker or its repository. Without one, default copyright applies: ask the author before reusing or redistributing it.
How many tokens does API Contract Checker use?
About 185 tokens (SKILL.md is roughly 740 characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.
What are the alternatives to API Contract Checker?
Skills that share tags, products or a category with API Contract Checker: Nodejs Backend Patterns (ever-works/ever-works, 162 stars), API Designer (Jeffallan/claude-skills, 12k stars), Pangolin CRUD Endpoints (fosrl/pangolin, 23k stars) and Backend Patterns (hellangleZ/burn-in-cceverywhere-ralph, 112 stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.
Who maintains API Contract Checker?
proflead (a GitHub user) maintains it in proflead/codex-skills-library, which has 155 GitHub stars. The repository holds 10 skills in this directory. The repository was last updated on July 29, 2026.
Source: proflead/codex-skills-library on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.