Validating API Contracts

What it does

When your agent uses it

• Performing specialized testing
• With phrases like validate API contract
• Run contract tests
• Check consumer contracts

Example prompts

• “validate API contract”
• “run contract tests”
• “check consumer contracts”
• “/validating-api-contracts”

Requirements

• Python 3
• A credential in PACT_BROKER_TOKEN
• Compatibility (from SKILL.md): Designed for Claude Code
• Pre-approved tools (allowed-tools): Read, Write, Edit, Grep, Glob, Bash(test:contract-*)

Workflow steps

7 steps, taken from the first numbered list in SKILL.md.

1. 1Identify consumer-provider relationships in the system
2. 2Write consumer-side contract tests (Pact consumer tests)
3. 3Publish consumer contracts to the Pact Broker
4. 4Write provider-side verification tests
5. 5Handle contract evolution
6. 6For schema-based validation (non-Pact)
7. 7Integrate contract tests into the CI/CD pipeline for both consumers and providers.

What it can do on your machine

Read from SKILL.md and the folder at commit 80f86df. It shows what the files ask for, not the result of running them.

• Tool permissions

  Pre-approves these tools, so the agent can use them without asking each time:

  • Read
  • Write
  • Edit
  • Grep
  • Glob
  • Bash(test:contract-*)

  From allowed-tools in the SKILL.md frontmatter.

• Runs code

  Ships 2 files in scripts/ (Python), which the agent can run.

  Shell commands in SKILL.md call:

  • git

  From the folder's file list and the shell code blocks in SKILL.md.

• Network

  Links to these hosts (documentation or services it may open):

  • docs.pact.io
  • pactflow.io
  • spring.io
  • github.com
  • martinfowler.com

  From URLs in SKILL.md, links to its own repository left out.

• Credentials

  Names these keys or tokens, usually read from environment variables:

  • PACT_BROKER_TOKEN

  From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

• Compatibility

  Designed for Claude Code

  From compatibility in the SKILL.md frontmatter.

Context cost

Validating API Contracts loads about 1.8k tokens when it runs, and up to ~1.8k if it reads all its reference files. Until then it costs about 66 tokens; SKILL.md has 550 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it

~66

When it runs · the whole SKILL.md, loaded when a task matches

~1.8k

With references · SKILL.md plus every file in references/, read only if the agent opens them

~1.8k

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

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); the scripts in this folder are not scanned.

SKILL.md

The full file from jeremylongshore/tons-of-skills-marketplace at commit 80f86df, republished under its MIT licence (© jeremylongshore). 550 words, ~1,772 tokens.

name

validating-api-contracts

description

Validate API contracts using consumer-driven contract testing (Pact, Spring Cloud Contract). Use when performing specialized testing. Trigger with phrases like "validate API contract", "run contract tests", or "check consumer contracts".

allowed-tools

Read, Write, Edit, Grep, Glob, Bash(test:contract-*)

compatibility

Designed for Claude Code

version

1.24.0

author

Jeremy Longshore <jeremy@intentsolutions.io>

license

MIT

tags

testing, api, validating-api

import { PactV4 } from '@pact-foundation/pact';

const provider = new PactV4({ consumer: 'Frontend', provider: 'UserAPI' });

describe('User API Contract', () => {
  it('fetches a user by ID', async () => {
    await provider
      .addInteraction()
      .given('user with ID 1 exists')
      .uponReceiving('a request for user 1')
      .withRequest('GET', '/api/users/1', (builder) => {
        builder.headers({ Accept: 'application/json' });
      })
      .willRespondWith(200, (builder) => {  # HTTP 200 OK
        builder
          .headers({ 'Content-Type': 'application/json' })
          .jsonBody({
            id: like('1'),
            name: like('Alice'),
            email: like('alice@example.com'),
          });
      })
      .executeTest(async (mockServer) => {
        const response = await fetch(`${mockServer.url}/api/users/1`);
        const user = await response.json();
        expect(user.name).toBeDefined();
      });
  });
});

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

describe('User API Provider Verification', () => {
  it('validates consumer contracts', async () => {
    await new Verifier({
      providerBaseUrl: 'http://localhost:3000',  # 3000: 3 seconds in ms
      pactBrokerUrl: process.env.PACT_BROKER_BASE_URL,
      pactBrokerToken: process.env.PACT_BROKER_TOKEN,
      provider: 'UserAPI',
      publishVerificationResult: true,
      providerVersion: process.env.GIT_SHA,
      stateHandlers: {
        'user with ID 1 exists': async () => {
          await db.users.create({ id: '1', name: 'Alice', email: 'alice@example.com' });
        },
      },
    }).verifyProvider();
  });
});

pact-broker can-i-deploy \
  --pacticipant Frontend \
  --version $(git rev-parse HEAD) \
  --to-environment production \
  --broker-base-url $PACT_BROKER_URL \
  --broker-token $PACT_BROKER_TOKEN

© jeremylongshore, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

SKILL.md and 8 other files (scripts, references, assets) in skills/.curated/validating-api-contracts of jeremylongshore/tons-of-skills-marketplace.

• SKILL.md
• assets/README.md
• assets/config_template.yaml
• assets/openapi_example.yaml
• assets/pact_contract_template.json
• assets/report_template.html
• references/README.md
• scripts/README.md
• scripts/generate_pact_tests.py

Open the folder on GitHubat commit 80f86df