API Testing
petrkindlmann/qa-skills
Test REST and GraphQL APIs with Playwright APIRequestContext, Supertest, or standalone HTTP clients.
REST and GraphQL testing, Postman/Insomnia patterns, contract testing, schema validation, and monitoring
Install API Testing
$ npx skills add cosmicstack-labs/mercury-agent-skills --skill api-testing -a claude-codeProject install by default; add -g for ~/.claude/skills/.
$ gh skill install cosmicstack-labs/mercury-agent-skills api-testing --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/cosmicstack-labs/mercury-agent-skills.git skills-src && mkdir -p .claude/skills && cp -r skills-src/categories/testing-qa/api-testing .claude/skills/api-testing && 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-testing" agent skill from https://github.com/cosmicstack-labs/mercury-agent-skills/tree/main/categories/testing-qa/api-testing into .claude/skills/api-testing/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "api-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 install https://github.com/cosmicstack-labs/mercury-agent-skills/tree/main/categories/testing-qa/api-testingType 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 cosmicstack-labs/mercury-agent-skills --skill api-testing -a codexProject install goes to .agents/skills/; add -g for ~/.codex/skills/.
$ gh skill install cosmicstack-labs/mercury-agent-skills api-testing --agent codexProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/cosmicstack-labs/mercury-agent-skills.git skills-src && mkdir -p .agents/skills && cp -r skills-src/categories/testing-qa/api-testing .agents/skills/api-testing && 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-testing" agent skill from https://github.com/cosmicstack-labs/mercury-agent-skills/tree/main/categories/testing-qa/api-testing into .agents/skills/api-testing/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "api-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.
$ npx skills add cosmicstack-labs/mercury-agent-skills --skill api-testing -a cursorProject install goes to .agents/skills/; add -g for ~/.cursor/skills/.
$ gh skill install cosmicstack-labs/mercury-agent-skills api-testing --agent cursorProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/cosmicstack-labs/mercury-agent-skills.git skills-src && mkdir -p .cursor/skills && cp -r skills-src/categories/testing-qa/api-testing .cursor/skills/api-testing && 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-testing" agent skill from https://github.com/cosmicstack-labs/mercury-agent-skills/tree/main/categories/testing-qa/api-testing into .cursor/skills/api-testing/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "api-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 https://github.com/cosmicstack-labs/mercury-agent-skills.git --path categories/testing-qa/api-testing--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 cosmicstack-labs/mercury-agent-skills --skill api-testing -a gemini-cliProject install goes to .agents/skills/; add -g for ~/.gemini/skills/.
$ gh skill install cosmicstack-labs/mercury-agent-skills api-testing --agent gemini-cliProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/cosmicstack-labs/mercury-agent-skills.git skills-src && mkdir -p .gemini/skills && cp -r skills-src/categories/testing-qa/api-testing .gemini/skills/api-testing && 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-testing" agent skill from https://github.com/cosmicstack-labs/mercury-agent-skills/tree/main/categories/testing-qa/api-testing into .gemini/skills/api-testing/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "api-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.
$ gh skill install cosmicstack-labs/mercury-agent-skills api-testingInstalls 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 cosmicstack-labs/mercury-agent-skills --skill api-testing -a github-copilotProject install goes to .agents/skills/; add -g for ~/.copilot/skills/.
$ git clone --depth 1 https://github.com/cosmicstack-labs/mercury-agent-skills.git skills-src && mkdir -p .github/skills && cp -r skills-src/categories/testing-qa/api-testing .github/skills/api-testing && 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-testing" agent skill from https://github.com/cosmicstack-labs/mercury-agent-skills/tree/main/categories/testing-qa/api-testing into .github/skills/api-testing/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "api-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.
$ npx skills add cosmicstack-labs/mercury-agent-skills --skill api-testing -a opencodeOpenCode documents no install command of its own. Project install goes to .agents/skills/; add -g for ~/.config/opencode/skills/.
$ gh skill install cosmicstack-labs/mercury-agent-skills api-testing --agent opencodeProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/cosmicstack-labs/mercury-agent-skills.git skills-src && mkdir -p .opencode/skills && cp -r skills-src/categories/testing-qa/api-testing .opencode/skills/api-testing && 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-testing" agent skill from https://github.com/cosmicstack-labs/mercury-agent-skills/tree/main/categories/testing-qa/api-testing into .opencode/skills/api-testing/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "api-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-testing- GitHub stars
- 476
- Token cost
- ~449 tokens
- SKILL.md length
- 121 words
- Files
- 1
- Skills in repo
- 12
- Repo updated
- First seen
- Licence
- MIT
At a glance
REST and GraphQL testing, Postman/Insomnia patterns, contract testing, schema validation, and monitoring
- Tasks that involve API testing
- SKILL.md covers Test Categories, REST API Testing, Contract Testing (Pact) and GraphQL Testing, plus 1 more section
- Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md
- Tasks that involve GraphQL
What it does
API Testing is an agent skill from cosmicstack-labs/mercury-agent-skills. REST and GraphQL testing, Postman/Insomnia patterns, contract testing, schema validation, and monitoring
Its SKILL.md is about 450 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 Testing & QA, covering API testing, GraphQL and Integration testing. It works with GraphQL and Postman. The repository describes itself as: A curated registry of reusable Mercury Agent, Open Claw or Hermes Agent skills designed for real developer workflows, persistent memory, and token-efficient execution. The licence is MIT.
When your agent uses it
- Tasks that involve API testing
- Tasks that involve GraphQL
- Tasks that involve Integration testing
Example prompts
- “/api-testing”
What it can do on your machine
Read from SKILL.md and the folder at commit 30392fb. 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).
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 Testing loads about 449 tokens when it runs. Until then it costs about 29 tokens; SKILL.md has 121 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
The full file from cosmicstack-labs/mercury-agent-skills at commit 30392fb, republished under its MIT licence (© cosmicstack-labs). 121 words, ~449 tokens.
Download SKILL.mdSave it as
.claude/skills/api-testing/SKILL.md (or your agent's skills folder).- name
- api-testing
- description
- REST and GraphQL testing, Postman/Insomnia patterns, contract testing, schema validation, and monitoring
- metadata.author
- cosmicstack-labs
- metadata.version
- 1.0.0
- metadata.category
- testing-qa
- metadata.tags
- api, testing, rest, graphql, contract-testing
API Testing
Test REST and GraphQL APIs systematically.
Test Categories
| Category | What | Example |
|---|---|---|
| Functional | Does it work? | POST /users returns 201 |
| Validation | Input handling | Missing required field → 400 |
| Auth | Access control | No token → 401 |
| Edge Cases | Boundary conditions | Max page size, empty results |
| Contract | Schema conformance | Response matches OpenAPI spec |
| Performance | Within SLO | p95 < 500ms |
REST API Testing
Structure
describe('POST /users', () => {
it('creates a user with valid data', async () => {
const res = await request(app)
.post('/api/users')
.send({ name: 'Alice', email: 'alice@test.com' });
expect(res.status).toBe(201);
expect(res.body).toHaveProperty('id');
});
it('rejects duplicate email', async () => {
const res = await request(app)
.post('/api/users')
.send({ name: 'Alice', email: 'existing@test.com' });
expect(res.status).toBe(409);
});
});Contract Testing (Pact)
- Provider publishes OpenAPI spec
- Consumer tests verify against published spec
- CI rejects PR if contract breaks
- Prevents API drift between services
GraphQL Testing
- Test queries and mutations independently
- Validate against schema
- Test error paths (partial failures, null propagation)
API Monitoring
- Synthetic checks every 5 minutes
- Assert status, response time, required fields
- Alert on SLA breaches
- Monitor from multiple regions
© cosmicstack-labs, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file
Files
Just SKILL.md in categories/testing-qa/api-testing of cosmicstack-labs/mercury-agent-skills.
Open the folder on GitHubat commit 30392fb
Compare with similar skills
API 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.
| Skill | Stars | Used in | Tokens | Auto-check | Licence | Repo updated |
|---|---|---|---|---|---|---|
| API Testing this skillcosmicstack-labs/mercury-agent-skills | 476 | — | ~449 | Automated safety check: Pass | MIT | |
| API Testingpetrkindlmann/qa-skills | 163 | — | ~2.7k | Automated safety check: Pass | MIT | |
| API Testingfugazi/test-automation-skills-agents | 247 | — | ~1.5k | Automated safety check: Pass | MIT | |
| Qe Contract Testingproffesor-for-testing/agentic-qe | 494 | — | ~1.2k | Automated safety check: Pass | MIT | |
| API Testingnaodeng/awesome-qa-skills | 243 | — | ~314 | Automated safety check: Pass | Custom licence | |
| Use Yaakmountain-loop/yaak | 19k | — | ~1.9k | Automated safety check: Pass | MIT |
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Related
Categories
Questions about API Testing
What does API Testing do?
REST and GraphQL testing, Postman/Insomnia patterns, contract testing, schema validation, and monitoring. API Testing is an agent skill from cosmicstack-labs/mercury-agent-skills.
When should I use API Testing?
API Testing fits situations like: tasks that involve API testing; tasks that involve GraphQL; tasks that involve Integration testing.
How do I install API Testing in Claude Code?
Run `npx skills add cosmicstack-labs/mercury-agent-skills --skill api-testing -a claude-code`. Or copy the skill folder (categories/testing-qa/api-testing in cosmicstack-labs/mercury-agent-skills) into .claude/skills/api-testing in your project. Claude Code loads it when a task matches its description.
How do I install API Testing in Codex?
Run `npx skills add cosmicstack-labs/mercury-agent-skills --skill api-testing -a codex`. Or copy the skill folder (categories/testing-qa/api-testing in cosmicstack-labs/mercury-agent-skills) into .agents/skills/api-testing in your project. Codex loads it when a task matches its description.
Can I use API 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 cosmicstack-labs/mercury-agent-skills --skill api-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-testing, .gemini/skills/api-testing, .github/skills/api-testing and .opencode/skills/api-testing in your project.
What does API Testing need to run?
SKILL.md names no scripts, command-line tools or credentials: API Testing is instructions for the agent only.
Does API 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 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 Testing use?
API Testing is published under the MIT licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.
How many tokens does API Testing use?
About 449 tokens (SKILL.md is roughly 1.8k 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 Testing?
Skills that share tags, products or a category with API Testing: API Testing (petrkindlmann/qa-skills, 163 stars), API Testing (fugazi/test-automation-skills-agents, 247 stars), Qe Contract Testing (proffesor-for-testing/agentic-qe, 494 stars) and API Testing (naodeng/awesome-qa-skills, 243 stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.
Who maintains API Testing?
cosmicstack-labs (a GitHub organization) maintains it in cosmicstack-labs/mercury-agent-skills, which has 476 GitHub stars. The repository holds 12 skills in this directory. The repository was last updated on August 25, 2026.
Source: cosmicstack-labs/mercury-agent-skills on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.