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Agent skill

API Designer

by revfactory in revfactory/harness-100

Full pipeline for REST/GraphQL API design, documentation, mocking, and testing.

Apache-2.0Auto-check passedBackend & APIs

Install API Designer

skills CLI
$ npx skills add revfactory/harness-100 --skill api-designer -a claude-code

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

GitHub CLI
$ gh skill install revfactory/harness-100 api-designer --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/revfactory/harness-100.git skills-src && mkdir -p .claude/skills && cp -r skills-src/en/18-api-designer/.claude/skills/api-designer .claude/skills/api-designer && 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/

Facts

Skill name
api-designer
GitHub stars
1.3k
Token cost
~1.8k tokens
SKILL.md length
689 words
Files
1
Skills in repo
464
Repo updated
First seen
Licence
Apache-2.0

At a glance

Full pipeline for REST/GraphQL API design, documentation, mocking, and testing.

  • Works in 3 steps: Preparation (Performed directly by the… → Team Assembly and Execution → Integration and Final Artifacts
  • Any API design task including design an API
  • SKILL.md covers Execution Mode, Agent Composition, Workflow and Mode by Task Scale, plus 4 more sections
  • Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md

What it does

API Designer is an agent skill from revfactory/harness-100. Full pipeline for REST/GraphQL API design, documentation, mocking, and testing. An agent team collaborates to perform API architecture design, OpenAPI/GraphQL schema generation, developer documentation writing, and mock server and test design. Use this skill for any API design task including 'design an API', 'REST API', 'GraphQL API', 'API documentation', 'API schema', 'OpenAPI', 'Swagger', 'API testing', 'API mocking', 'endpoint design', etc. Also supports documentation and testing for existing APIs. Note…

Its SKILL.md is about 1.8k 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, OpenAPI specifications and GraphQL. It works with GraphQL, OpenAPI and FastAPI. The licence is Apache-2.0.

When your agent uses it

  • Any API design task including design an API
  • API documentation
  • Endpoint design

Example prompts

  • “design an API”
  • “REST API”
  • “GraphQL API”
  • “/api-designer”

Workflow steps

3 steps, taken from the step headings in SKILL.md.

  1. Preparation (Performed directly by the orchestrator)
  2. Team Assembly and Execution
  3. Integration and Final Artifacts

What it can do on your machine

Read from SKILL.md and the folder at commit 8e8d35c. 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 Designer loads about 1.8k tokens when it runs. Until then it costs about 168 tokens; SKILL.md has 689 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~168
When it runs · the whole SKILL.md, loaded when a task matches
~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

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 revfactory/harness-100 at commit 8e8d35c, republished under its Apache-2.0 licence (© revfactory). 689 words, ~1,754 tokens.

Download SKILL.mdSave it as .claude/skills/api-designer/SKILL.md (or your agent's skills folder).
name
api-designer
description
Full pipeline for REST/GraphQL API design, documentation, mocking, and testing. An agent team collaborates to perform API architecture design, OpenAPI/GraphQL schema generation, developer documentation writing, and mock server and test design. Use this skill for any API design task including 'design an API', 'REST API', 'GraphQL API', 'API documentation', 'API schema', 'OpenAPI', 'Swagger', 'API testing', 'API mocking', 'endpoint design', etc. Also supports documentation and testing for existing APIs. Note: actual server implementation (Express, FastAPI, etc.), API Gateway deployment, and monitoring dashboard setup are outside the scope of this skill.

API Designer — API Design, Documentation, Mocking, and Testing Pipeline

An agent team collaborates to generate API design, schema, documentation, and mock/tests in a single pass.

Execution Mode

Agent Team — 5 members communicate directly via SendMessage and cross-validate each other's work.

Agent Composition

AgentFileRoleType
api-architect.claude/agents/api-architect.mdResource modeling, endpoints, versioninggeneral-purpose
schema-validator.claude/agents/schema-validator.mdOpenAPI/GraphQL schema, type validationgeneral-purpose
doc-writer.claude/agents/doc-writer.mdDeveloper documentation, examples, error referencesgeneral-purpose
mock-tester.claude/agents/mock-tester.mdMock server, integration tests, load scenariosgeneral-purpose
review-auditor.claude/agents/review-auditor.mdSecurity, consistency, performance, alignment validationgeneral-purpose

Workflow

Phase 1: Preparation (Performed directly by the orchestrator)
  1. Extract from user input:
    • Domain: What service is the API for
    • Paradigm: REST / GraphQL / Hybrid
    • Key Resources: List of core entities
    • Authentication Method (optional): OAuth, JWT, API Key
    • Existing Files (optional): Existing schemas, documentation, code, etc.
  2. Create the _workspace/ directory at the project root
  3. Organize the input and save to _workspace/00_input.md
  4. If existing files are provided, copy them to _workspace/ and skip the corresponding phase
  5. Determine the execution mode based on the scope of the request
Phase 2: Team Assembly and Execution
OrderTaskOwnerDependenciesArtifact
1API Designapi-architectNone_workspace/01_api_design.md
2Schema Generation & Validationschema-validatorTask 1_workspace/02_schema.yaml, 02_schema_validation.md
3aAPI Documentationdoc-writerTasks 1, 2_workspace/03_api_docs.md
3bMock Server & Testsmock-testerTasks 1, 2_workspace/04_mock_tests.md
4API Reviewreview-auditorTasks 2, 3a, 3b_workspace/05_review_report.md

Tasks 3a (documentation) and 3b (tests) are executed in parallel.

Inter-team communication flow:

  • api-architect completes -> Delivers resource model to schema-validator, endpoints to doc-writer, request/response examples to mock-tester
  • schema-validator completes -> Delivers schema to doc-writer, schema-based examples to mock-tester
  • doc-writer <-> mock-tester: Mutually verify that documentation examples and mock responses match
  • review-auditor cross-validates all artifacts. When 🔴 must-fix issues are found, requests revisions from the relevant agent -> rework -> re-verify (up to 2 rounds)
Phase 3: Integration and Final Artifacts

Organize the final artifacts based on the review report:

  1. Verify all files in _workspace/
  2. Confirm that all 🔴 must-fix items from the review report have been addressed
  3. Report the final summary to the user

Mode by Task Scale

User Request PatternExecution ModeAgents Deployed
"Design an API", "full design"Full PipelineAll 5 agents
"Just write API docs" (existing API)Documentation Modedoc-writer + review-auditor
"Validate this OpenAPI schema"Validation Modeschema-validator + review-auditor
"Design API tests" (existing schema)Test Modemock-tester + review-auditor
"Review this API design"Review Modereview-auditor only

Leveraging existing files: If the user provides schemas, documentation, or other existing files, skip the corresponding steps.

Show full SKILL.md (278 more words)Show less

Data Transfer Protocol

StrategyMethodPurpose
File-based_workspace/ directoryStore and share primary artifacts
Message-basedSendMessageReal-time delivery of key information, revision requests
Task-basedTaskCreate/TaskUpdateProgress tracking, dependency management

File naming convention: {order}_{agent}_{artifact}.{extension}

Error Handling

Error TypeStrategy
Insufficient domain informationAPI architect starts with generic CRUD resources; designs an extensible structure
REST vs GraphQL undecidedDefault to REST; present GraphQL extension options in an appendix
Agent failureRetry once -> If still fails, proceed without that artifact; note the omission in the review report
🔴 found during reviewRequest revision from the relevant agent -> rework -> re-verify (up to 2 rounds)
Existing schema parsing failureManually extract endpoints and proceed

Test Scenarios

Normal Flow

Prompt: "Design a REST API for an e-commerce platform. I need product, order, user, and cart resources" Expected Result:

  • API Design: 4 resources, CRUD endpoints, relationship modeling, authentication design
  • Schema: OpenAPI 3.1 YAML, all model type definitions
  • Documentation: Quick start + endpoint reference + error codes
  • Tests: Per-resource CRUD tests + authentication tests + load scenarios
  • Review: All items in the alignment matrix verified
Existing File Flow

Prompt: "Create API docs and tests from this OpenAPI schema" + schema file Expected Result:

  • Copy existing schema to _workspace/02_schema.yaml
  • Merged documentation + test mode: deploy doc-writer + mock-tester + review-auditor
  • Skip api-architect and schema-validator
Error Flow

Prompt: "Design an API quickly, blog platform" Expected Result:

  • Insufficient domain information -> api-architect infers standard blog resources (Post, Comment, User, Tag)
  • Execute in full pipeline mode
  • Review report notes "design based on inferred domain requirements"

Agent Extension Skills

Extension skills that enhance each agent's domain expertise:

SkillTarget AgentRole
rest-api-conventionsapi-architectURL naming, HTTP status codes, pagination, versioning
api-error-designdoc-writer, mock-testerError code systems, error response structures, retry/fallback strategies

© revfactory, Apache-2.0. 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 en/18-api-designer/.claude/skills/api-designer of revfactory/harness-100.

Open the folder on GitHubat commit 8e8d35c

Compare with similar skills

API Designer 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 Designer compared with similar skills
SkillStarsUsed inTokensAuto-checkLicenceRepo updated
API Designer this skillrevfactory/harness-1001.3k—~1.8kAutomated safety check: PassApache-2.0
API Designericrisco/rsc-harness156—~3.1kAutomated safety check: PassMIT
API DesignerJeffallan/claude-skills12k2 repos~2kAutomated safety check: PassMIT
API Designyonatangross/orchestkit288—~2.9kAutomated safety check: PassMIT
API Contract Detectionprime-radiant-inc/greenfield292—~4.2kAutomated safety check: PassApache-2.0
Implementing API Patternsancoleman/ai-design-components5261 repos~3kAutomated safety check: PassMIT

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Works with

Categories

Questions about API Designer

What does API Designer do?

Full pipeline for REST/GraphQL API design, documentation, mocking, and testing. API Designer is an agent skill from revfactory/harness-100. Full pipeline for REST/GraphQL API design, documentation, mocking, and testing.

When should I use API Designer?

API Designer fits situations like: any API design task including design an API; API documentation; endpoint design.

How do I install API Designer in Claude Code?

Run `npx skills add revfactory/harness-100 --skill api-designer -a claude-code`. Or copy the skill folder (en/18-api-designer/.claude/skills/api-designer in revfactory/harness-100) into .claude/skills/api-designer in your project. Claude Code loads it when a task matches its description.

How do I install API Designer in Codex?

Run `npx skills add revfactory/harness-100 --skill api-designer -a codex`. Or copy the skill folder (en/18-api-designer/.claude/skills/api-designer in revfactory/harness-100) into .agents/skills/api-designer in your project. Codex loads it when a task matches its description.

Can I use API Designer 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 revfactory/harness-100 --skill api-designer -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-designer, .gemini/skills/api-designer, .github/skills/api-designer and .opencode/skills/api-designer in your project.

What does API Designer need to run?

SKILL.md names no scripts, command-line tools or credentials: API Designer is instructions for the agent only.

Does API Designer 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 Designer 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 Designer use?

API Designer is published under the Apache-2.0 licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does API Designer use?

About 1.8k tokens (SKILL.md is roughly 7k 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 Designer?

Skills that share tags, products or a category with API Designer: API Design (ericrisco/rsc-harness, 156 stars), API Designer (Jeffallan/claude-skills, 12k stars), API Design (yonatangross/orchestkit, 288 stars) and API Contract Detection (prime-radiant-inc/greenfield, 292 stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains API Designer?

revfactory (a GitHub user) maintains it in revfactory/harness-100, which has 1,290 GitHub stars. The repository holds 464 skills in this directory. The repository was last updated on March 22, 2026.

Source: revfactory/harness-100 on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.