Agent skill

API Contract Testing

Verifies API contracts between services using consumer-driven contracts, schema validation, and tools like Pact.

Install API Contract Testing

skills CLI

$ npx skills add secondsky/claude-skills --skill api-contract-testing -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI

$ gh skill install secondsky/claude-skills api-contract-testing --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy

$ git clone --depth 1 https://github.com/secondsky/claude-skills.git skills-src && mkdir -p .claude/skills && cp -r skills-src/plugins/api-contract-testing/skills/api-contract-testing .claude/skills/api-contract-testing && rm -rf skills-src

Use ~/.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/

Paste into Claude Code

Install the "api-contract-testing" agent skill from https://github.com/secondsky/claude-skills/tree/main/plugins/api-contract-testing/skills/api-contract-testing into .claude/skills/api-contract-testing/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "api-contract-testing", 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

$skill-installer install https://github.com/secondsky/claude-skills/tree/main/plugins/api-contract-testing/skills/api-contract-testing

Type 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.

skills CLI

$ npx skills add secondsky/claude-skills --skill api-contract-testing -a codex

Project install goes to .agents/skills/; add -g for ~/.codex/skills/.

GitHub CLI

$ gh skill install secondsky/claude-skills api-contract-testing --agent codex

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/secondsky/claude-skills.git skills-src && mkdir -p .agents/skills && cp -r skills-src/plugins/api-contract-testing/skills/api-contract-testing .agents/skills/api-contract-testing && rm -rf skills-src

Use ~/.agents/skills/ instead of .agents/skills for a personal install.

Codex skills documentation · loads skills from .agents/skills/

Paste into Codex

Install the "api-contract-testing" agent skill from https://github.com/secondsky/claude-skills/tree/main/plugins/api-contract-testing/skills/api-contract-testing into .agents/skills/api-contract-testing/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "api-contract-testing", 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.

skills CLI

$ npx skills add secondsky/claude-skills --skill api-contract-testing -a cursor

Project install goes to .agents/skills/; add -g for ~/.cursor/skills/.

GitHub CLI

$ gh skill install secondsky/claude-skills api-contract-testing --agent cursor

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/secondsky/claude-skills.git skills-src && mkdir -p .cursor/skills && cp -r skills-src/plugins/api-contract-testing/skills/api-contract-testing .cursor/skills/api-contract-testing && rm -rf skills-src

Use ~/.cursor/skills/ instead of .cursor/skills for a personal install.

Cursor skills documentation · loads skills from .cursor/skills/, .agents/skills/, .claude/skills/, .codex/skills/

Paste into Cursor

Install the "api-contract-testing" agent skill from https://github.com/secondsky/claude-skills/tree/main/plugins/api-contract-testing/skills/api-contract-testing into .cursor/skills/api-contract-testing/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "api-contract-testing", 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

$ gemini skills install https://github.com/secondsky/claude-skills.git --path plugins/api-contract-testing/skills/api-contract-testing

--scope user (default) or --scope workspace; --path is the subfolder of the repo that holds the skill; --consent skips the security confirmation prompt.

skills CLI

$ npx skills add secondsky/claude-skills --skill api-contract-testing -a gemini-cli

Project install goes to .agents/skills/; add -g for ~/.gemini/skills/.

GitHub CLI

$ gh skill install secondsky/claude-skills api-contract-testing --agent gemini-cli

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/secondsky/claude-skills.git skills-src && mkdir -p .gemini/skills && cp -r skills-src/plugins/api-contract-testing/skills/api-contract-testing .gemini/skills/api-contract-testing && rm -rf skills-src

Use ~/.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/

Paste into Gemini CLI

Install the "api-contract-testing" agent skill from https://github.com/secondsky/claude-skills/tree/main/plugins/api-contract-testing/skills/api-contract-testing into .gemini/skills/api-contract-testing/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "api-contract-testing", 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.

GitHub CLI

$ gh skill install secondsky/claude-skills api-contract-testing

Installs 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).

skills CLI

$ npx skills add secondsky/claude-skills --skill api-contract-testing -a github-copilot

Project install goes to .agents/skills/; add -g for ~/.copilot/skills/.

Manual copy

$ git clone --depth 1 https://github.com/secondsky/claude-skills.git skills-src && mkdir -p .github/skills && cp -r skills-src/plugins/api-contract-testing/skills/api-contract-testing .github/skills/api-contract-testing && rm -rf skills-src

Use ~/.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/

Paste into GitHub Copilot

Install the "api-contract-testing" agent skill from https://github.com/secondsky/claude-skills/tree/main/plugins/api-contract-testing/skills/api-contract-testing into .github/skills/api-contract-testing/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "api-contract-testing", 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.

skills CLI

$ npx skills add secondsky/claude-skills --skill api-contract-testing -a opencode

OpenCode documents no install command of its own. Project install goes to .agents/skills/; add -g for ~/.config/opencode/skills/.

GitHub CLI

$ gh skill install secondsky/claude-skills api-contract-testing --agent opencode

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/secondsky/claude-skills.git skills-src && mkdir -p .opencode/skills && cp -r skills-src/plugins/api-contract-testing/skills/api-contract-testing .opencode/skills/api-contract-testing && rm -rf skills-src

Use ~/.config/opencode/skills/ instead of .opencode/skills for a personal install.

OpenCode skills documentation · loads skills from .opencode/skills/, .claude/skills/, .agents/skills/

Paste into OpenCode

Install the "api-contract-testing" agent skill from https://github.com/secondsky/claude-skills/tree/main/plugins/api-contract-testing/skills/api-contract-testing into .opencode/skills/api-contract-testing/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "api-contract-testing", 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-testing
GitHub stars: 227
Token cost: ~977 tokens
SKILL.md length: 148 words
Files: 4 (incl. references)
Skills in repo: 169
Repo updated: Sep 28, 2026
First seen: Oct 7, 2026
Licence: MIT

At a glance

Verifies API contracts between services using consumer-driven contracts, schema validation, and tools like Pact.

Testing microservices communication
SKILL.md covers Key Concepts, Pact Consumer Test (TypeScript), Provider Verification and OpenAPI Validation (Express), plus 3 more sections
Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md
Preventing breaking changes

What it does

API Contract Testing is an agent skill from secondsky/claude-skills. Verifies API contracts between services using consumer-driven contracts, schema validation, and tools like Pact. Use when testing microservices communication, preventing breaking changes, or validating OpenAPI specifications.

Its SKILL.md is about 980 tokens, which your agent loads only when the skill is triggered. The skill folder holds 4 other files, including reference files (for example `references/java-rest-assured.md`, `references/pact-broker-cicd.md` and `references/python-json-schema.md`).

It sits in Backend & APIs, covering API design, OpenAPI specifications and Forms and validation. It works with OpenAPI, Java and Python. The repository describes itself as: Production-ready skills for Claude Code CLI - Cloudflare, React, Tailwind v4, and AI integrations. The licence is MIT.

When your agent uses it

Testing microservices communication
Preventing breaking changes
Validating OpenAPI specifications

Example prompts

“Use the api-contract-testing skill to verify API contracts between services using consumer-driven contracts, schema validation, and tools like Pact”
“/api-contract-testing”

Requirements

Python 3

What it can do on your machine

Read from SKILL.md and the folder at commit 8837836. 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 (its code samples are typescript and javascript).
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 Testing loads about 977 tokens when it runs, and up to ~6.3k if it reads all its reference files. Until then it costs about 62 tokens; SKILL.md has 148 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it: ~62
When it runs · the whole SKILL.md, loaded when a task matches: ~977
With references · SKILL.md plus every file in references/, read only if the agent opens them: ~6.3k

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

The full file from secondsky/claude-skills at commit 8837836, republished under its MIT licence (© secondsky). 148 words, ~977 tokens.

Download SKILL.mdSave it as .claude/skills/api-contract-testing/SKILL.md (or your agent's skills folder). This skill also uses 3 other files; get the full folder from GitHub.

name: api-contract-testing
description: Verifies API contracts between services using consumer-driven contracts, schema validation, and tools like Pact. Use when testing microservices communication, preventing breaking changes, or validating OpenAPI specifications.
license: MIT

API Contract Testing

Verify that APIs honor their contracts between consumers and providers without requiring full integration tests.

Key Concepts

Term	Definition
Consumer	Service that calls an API
Provider	Service that exposes an API
Contract	Agreed request/response format
Pact	Consumer-driven contract testing tool
Schema	Structure definition (OpenAPI, JSON Schema)
Broker	Central repository for contracts

Pact Consumer Test (TypeScript)

typescript

import { PactV3, MatchersV3 } from '@pact-foundation/pact';

const provider = new PactV3({
  consumer: 'OrderService',
  provider: 'UserService'
});

describe('User API Contract', () => {
  it('returns user by ID', async () => {
    await provider
      .given('user 123 exists')
      .uponReceiving('a request for user 123')
      .withRequest({ method: 'GET', path: '/users/123' })
      .willRespondWith({
        status: 200,
        body: MatchersV3.like({
          id: '123',
          name: MatchersV3.string('John'),
          email: MatchersV3.email('john@example.com')
        })
      })
      .executeTest(async (mockServer) => {
        const response = await fetch(`${mockServer.url}/users/123`);
        expect(response.status).toBe(200);
      });
  });

  it('returns 404 for non-existent user', async () => {
    await provider
      .given('user does not exist')
      .uponReceiving('a request for non-existent user')
      .withRequest({ method: 'GET', path: '/users/999' })
      .willRespondWith({
        status: 404,
        body: MatchersV3.like({
          error: { code: 'NOT_FOUND', message: MatchersV3.string() }
        })
      })
      .executeTest(async (mockServer) => {
        const response = await fetch(`${mockServer.url}/users/999`);
        expect(response.status).toBe(404);
      });
  });
});

Provider Verification

typescript

import { Verifier } from '@pact-foundation/pact';

new Verifier({
  provider: 'UserService',
  providerBaseUrl: 'http://localhost:3000',
  pactBrokerUrl: process.env.PACT_BROKER_URL,
  publishVerificationResult: true,
  providerVersion: process.env.GIT_SHA,
  stateHandlers: {
    'user 123 exists': async () => {
      await db.users.create({ id: '123', name: 'John' });
    },
    'user does not exist': async () => {
      await db.users.deleteAll();
    }
  }
}).verifyProvider();

OpenAPI Validation (Express)

javascript

const OpenApiValidator = require('express-openapi-validator');

app.use(OpenApiValidator.middleware({
  apiSpec: './openapi.yaml',
  validateRequests: true,
  validateResponses: true,
  validateSecurity: true
}));

Additional Implementations

Python JSON Schema: See references/python-json-schema.md
Java REST Assured: See references/java-rest-assured.md
Pact Broker CI/CD: See references/pact-broker-cicd.md

Best Practices

Do:

Test from consumer perspective
Use matchers for flexible matching
Validate structure, not specific values
Version contracts explicitly
Test error responses
Run tests in CI pipeline
Test backward compatibility

Don't:

Test business logic in contracts
Hard-code specific values
Skip error scenarios
Ignore versioning
Deploy without verification

Tools

Pact - Multi-language consumer-driven contracts
Spring Cloud Contract - JVM ecosystem
OpenAPI/Swagger - Schema-first validation
Dredd - API blueprint testing
Spectral - OpenAPI linting

Files

SKILL.md and 3 other files (references) in plugins/api-contract-testing/skills/api-contract-testing of secondsky/claude-skills.

SKILL.md
references/java-rest-assured.md
references/pact-broker-cicd.md
references/python-json-schema.md

Open the folder on GitHubat commit 8837836

Compare with similar skills

API Contract Testing 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.

API Contract Testing compared with similar skills
Skill	Stars	Used in	Tokens	Auto-check	Licence	Repo updated
API Contract Testing this skillsecondsky/claude-skills	227	—	~977	Automated safety check: Pass	MIT	10 days ago
API Contract Openapimakifbaysal/tasktrooper	109	—	~1.2k	Automated safety check: Pass	Apache-2.0	today
Yapi Skillhashgraph-online/awesome-codex-plugins	1.2k	—	~2k	Automated safety check: Pass	Apache-2.0	today
703 Technologies Fuzzing Testingjabrena/plinth	446	—	~874	Automated safety check: Pass	Apache-2.0	yesterday
Agentic Workflows API Documentation Lungoagntcy/coffeeAgntcy	112	—	~2.6k	Automated safety check: Pass	Apache-2.0	yesterday
API DesignerJeffallan/claude-skills	12k	2 repos	~2k	Automated safety check: Pass	MIT	5 days ago

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Works with

Questions about API Contract Testing

What does API Contract Testing do?

Verifies API contracts between services using consumer-driven contracts, schema validation, and tools like Pact. API Contract Testing is an agent skill from secondsky/claude-skills. Verifies API contracts between services using consumer-driven contracts, schema validation, and tools like Pact.

When should I use API Contract Testing?

API Contract Testing fits situations like: testing microservices communication; preventing breaking changes; validating OpenAPI specifications.

How do I install API Contract Testing in Claude Code?

Run `npx skills add secondsky/claude-skills --skill api-contract-testing -a claude-code`. Or copy the skill folder (plugins/api-contract-testing/skills/api-contract-testing in secondsky/claude-skills) into .claude/skills/api-contract-testing in your project. Claude Code loads it when a task matches its description.

How do I install API Contract Testing in Codex?

Run `npx skills add secondsky/claude-skills --skill api-contract-testing -a codex`. Or copy the skill folder (plugins/api-contract-testing/skills/api-contract-testing in secondsky/claude-skills) into .agents/skills/api-contract-testing in your project. Codex loads it when a task matches its description.

Can I use API Contract Testing 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 secondsky/claude-skills --skill api-contract-testing -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-testing, .gemini/skills/api-contract-testing, .github/skills/api-contract-testing and .opencode/skills/api-contract-testing in your project.

What does API Contract Testing need to run?

SKILL.md names no scripts, command-line tools or credentials: API Contract Testing is instructions for the agent only. Our summary lists: Python 3.

Does API Contract Testing 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 Testing 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 Testing use?

API Contract Testing is published under the MIT licence (declared in SKILL.md). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does API Contract Testing use?

About 977 tokens (SKILL.md is roughly 3.9k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full. Its references folder adds about 5.3k tokens, read only when the agent opens those files.

What are the alternatives to API Contract Testing?

Skills that share tags, products or a category with API Contract Testing: API Contract Openapi (makifbaysal/tasktrooper, 109 stars), Yapi Skill (hashgraph-online/awesome-codex-plugins, 1.2k stars), 703 Technologies Fuzzing Testing (jabrena/plinth, 446 stars) and Agentic Workflows API Documentation Lungo (agntcy/coffeeAgntcy, 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 Testing?

secondsky (a GitHub user) maintains it in secondsky/claude-skills, which has 227 GitHub stars. The repository holds 169 skills in this directory. The repository was last updated on September 28, 2026.

Source: secondsky/claude-skills on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.

Install API Contract Testing

Facts

At a glance

What it does

When your agent uses it

Example prompts

Requirements

What it can do on your machine

Tool permissions

Runs code

Network

Credentials

Context cost

Safety

SKILL.md

API Contract Testing

Key Concepts

Pact Consumer Test (TypeScript)

Provider Verification

OpenAPI Validation (Express)

Additional Implementations

Best Practices

Tools

Files

Compare with similar skills

Similar skills

More from secondsky/claude-skills

Related

Questions about API Contract Testing