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Agent skill

API Contract Openapi

by makifbaysal in makifbaysal/tasktrooper

A skill your agent uses when you add or change any HTTP endpoint's request or response shape (Go or Java) — implement the task's contract exactly, evolve additively, keep the OpenAPI document in…

Apache-2.0Auto-check passedBackend & APIs

Install API Contract Openapi

skills CLI
$ npx skills add makifbaysal/tasktrooper --skill api-contract-openapi -a claude-code

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

GitHub CLI
$ gh skill install makifbaysal/tasktrooper api-contract-openapi --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/makifbaysal/tasktrooper.git skills-src && mkdir -p .claude/skills && cp -r skills-src/catalog/agents/backend-developer/skills/api-contract-openapi .claude/skills/api-contract-openapi && 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-contract-openapi
GitHub stars
109
Token cost
~1.2k tokens
SKILL.md length
585 words
Files
1
Skills in repo
99
Repo updated
First seen
Licence
Apache-2.0

At a glance

A skill your agent uses when you add or change any HTTP endpoint's request or response shape (Go or Java) — implement the task's contract exactly, evolve additively, keep the OpenAPI document in…

  • Works in 3 steps: Add name alongside title in the… → add_task_comment naming the consumer… → In a later task — once the architect…
  • Change any HTTP endpoints request
  • SKILL.md covers Overview, Your task's contract is…, Detect the spec source and Additive vs breaking, plus 5 more sections
  • Calls git, go and npx

What it does

API Contract Openapi is an agent skill from makifbaysal/tasktrooper. Use when you add or change any HTTP endpoint's request or response shape (Go or Java) — implement the task's contract exactly, evolve additively, keep the OpenAPI document in sync, and detect breaking changes before hand-off

Its SKILL.md is about 1.2k 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 OpenAPI specifications and API design. It works with OpenAPI and Java. The repository describes itself as: Local-first agent platform: board + role agents + agent CLI runs (Claude Code, Cursor, Antigravity, OpenCode) or local and API models (Ollama, LM Studio), all on your own Mac. The licence is Apache-2.0.

When your agent uses it

  • Change any HTTP endpoints request
  • Response shape (Go
  • Java) — implement the tasks contract exactly
  • Evolve additively

Example prompts

  • “s request or response shape (Go or Java) — implement the task”
  • “/api-contract-openapi”

Requirements

  • Node.js

Workflow steps

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

  1. Add name alongside title in the response; populate both. Document title as deprecated in the spec.
  2. add_task_comment naming the consumer task(s)/component(s) that must switch to name.
  3. In a later task — once the architect confirms no consumer reads title — remove it with a contract note.

What it can do on your machine

Read from SKILL.md and the folder at commit 09f6258. 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

    Shell commands in SKILL.md call:

    • git
    • go
    • npx

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

  • Network

    No URLs in SKILL.md. Its commands use git and npx, which can reach the network depending on how they are called.

    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 Openapi loads about 1.2k tokens when it runs. Until then it costs about 61 tokens; SKILL.md has 585 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~61
When it runs · the whole SKILL.md, loaded when a task matches
~1.2k

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 makifbaysal/tasktrooper at commit 09f6258, republished under its Apache-2.0 licence (© makifbaysal). 585 words, ~1,163 tokens.

Download SKILL.mdSave it as .claude/skills/api-contract-openapi/SKILL.md (or your agent's skills folder).
name
api-contract-openapi
description
Use when you add or change any HTTP endpoint's request or response shape (Go or Java) — implement the task's contract exactly, evolve additively, keep the OpenAPI document in sync, and detect breaking changes before hand-off
category
api

OpenAPI & API Contracts

Overview

The API contract is a promise the web and mobile clients depend on. A silent shape change (renamed field, changed type, removed endpoint) compiles fine on the backend and breaks every consumer at runtime.

Core principle: the contract is the annotation + DTO in code. Implement the task's contract exactly, evolve it additively, and never edit a consumer yourself.

Your task's contract is already copied into the consumer tasks

Your task's Interfaces / contract block is already copied, word for word, into the consumer tasks (the architect writes it once and copies it to the frontend and mobile tasks, which are blocked_by and deploy_depends_on yours). Implement it exactly: path, method, field names and casing, types, status codes. A shape you think is better is a comment on your task, not a change.

Consumers are not yours to edit. Find them with list_links (direction in) and grep_code for the path or field. Another component's or repository's client code belongs to its own task, and cross-repository actions are refused. Keep your change additive. When a breaking change is truly required, add_task_comment naming every consumer task or component and what each must change, and stop short of the break.

Detect the spec source

SignalTooling
//@Summary///@Router commentsswaggo (swag init; v1 emits Swagger 2.0 only)
openapi.yaml/.json + generated server stubsoapi-codegen (spec-first, go generate ./...)
Go struct tags driving a schema, no annotationshuma or ogen
@Operation/@Schema on JAX-RS resourcesspringdoc-openapi / quarkus-smallrye-openapi — spec is generated at runtime; snapshot it at /q/openapi or /v3/api-docs
A hand-maintained openapi.yaml with no generatoredit it directly

Keep the document's existing OpenAPI version (3.0/3.1/3.2 all current); upgrading the spec version is never part of a feature task.

Additive vs breaking

ChangeTypeAction
Add optional fieldAdditiveSafe; document it
Add required request fieldBreakingCoordinate via the task's contract, never edit callers yourself
Rename fieldBreakingPrefer add-new + deprecate-old
Change field typeBreakingNew field or coordinated cutover
Remove endpoint/fieldBreakingDeprecate first, remove later

Breaking-change check

Diff the spec against the merge base before you finish:

mkdir -p /tmp/tt-<task key> && git show "$(git merge-base HEAD origin/HEAD)":api/openapi.yaml > /tmp/tt-<task key>/base.yaml
go run github.com/oasdiff/oasdiff@latest breaking /tmp/tt-<task key>/base.yaml api/openapi.yaml

It must print nothing unless the task is the planned break. Lint with npx --yes @redocly/cli lint api/openapi.yaml when the repo has no linter already wired in.

Show full SKILL.md (218 more words)Show less

Every endpoint documented

Request/response schema, every status code it can return (including the error shape — see api-design-conventions), and pagination parameters where the endpoint lists anything.

Worked Example

Task's contract: POST /tasks returns {id, title, status}. A later task wants to rename title to name for a different repository's consumer.

Wrong: rename the DTO field and ship — every client reading title breaks, and your task has no authority to touch their code.

Right (additive cutover):

  1. Add name alongside title in the response; populate both. Document title as deprecated in the spec.
  2. add_task_comment naming the consumer task(s)/component(s) that must switch to name.
  3. In a later task — once the architect confirms no consumer reads title — remove it with a contract note.

Each step keeps every consumer green and respects task boundaries.

Common Mistakes

  • Implementing a shape you think is cleaner instead of the task's Interfaces block verbatim.
  • Editing a consumer's client code because it was easy to find.
  • A required new request field added with no coordinated consumer task.
  • Spec left stale after a handler change, or oasdiff never run.

Red Flags

  • A DTO field renamed or removed with oasdiff breaking printing output.
  • A diff that touches files outside your component/repository to "fix" a client.
  • A consumer reading a field the backend just removed, with no deprecation step.

© makifbaysal, 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 catalog/agents/backend-developer/skills/api-contract-openapi of makifbaysal/tasktrooper.

Open the folder on GitHubat commit 09f6258

Compare with similar skills

API Contract Openapi 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 Openapi compared with similar skills
SkillStarsUsed inTokensAuto-checkLicenceRepo updated
API Contract Openapi this skillmakifbaysal/tasktrooper109—~1.2kAutomated safety check: PassApache-2.0
API Contract Testingsecondsky/claude-skills227—~977Automated safety check: PassMIT
703 Technologies Fuzzing Testingjabrena/plinth446—~874Automated safety check: PassApache-2.0
API DesignerJeffallan/claude-skills12k2 repos~2kAutomated safety check: PassMIT
Old Coder API DesignAmazingAng/old-coder7491 repos~3.4kAutomated safety check: PassMIT
API Surface Reviewpolarsource/polar10k—~1.3kAutomated safety check: PassMIT

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  • Analiz Gate

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Works with

Categories

Questions about API Contract Openapi

What does API Contract Openapi do?

A skill your agent uses when you add or change any HTTP endpoint's request or response shape (Go or Java) — implement the task's contract exactly, evolve additively, keep the OpenAPI document in…. API Contract Openapi is an agent skill from makifbaysal/tasktrooper.

When should I use API Contract Openapi?

API Contract Openapi fits situations like: change any HTTP endpoints request; response shape (Go; java) — implement the tasks contract exactly; evolve additively.

How do I install API Contract Openapi in Claude Code?

Run `npx skills add makifbaysal/tasktrooper --skill api-contract-openapi -a claude-code`. Or copy the skill folder (catalog/agents/backend-developer/skills/api-contract-openapi in makifbaysal/tasktrooper) into .claude/skills/api-contract-openapi in your project. Claude Code loads it when a task matches its description.

How do I install API Contract Openapi in Codex?

Run `npx skills add makifbaysal/tasktrooper --skill api-contract-openapi -a codex`. Or copy the skill folder (catalog/agents/backend-developer/skills/api-contract-openapi in makifbaysal/tasktrooper) into .agents/skills/api-contract-openapi in your project. Codex loads it when a task matches its description.

Can I use API Contract Openapi 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 makifbaysal/tasktrooper --skill api-contract-openapi -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-openapi, .gemini/skills/api-contract-openapi, .github/skills/api-contract-openapi and .opencode/skills/api-contract-openapi in your project.

What does API Contract Openapi need to run?

Going by SKILL.md and its folder, API Contract Openapi needs the command-line tools its instructions call (git, go and npx). Our summary lists: Node.js.

Does API Contract Openapi access the network?

SKILL.md contains no URLs. Its commands use git and npx, which can reach the network depending on how they are called. This is read from the text; nothing was executed.

Is API Contract Openapi 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 Openapi use?

API Contract Openapi 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 Contract Openapi use?

About 1.2k tokens (SKILL.md is roughly 4.7k 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 Contract Openapi?

Skills that share tags, products or a category with API Contract Openapi: API Contract Testing (secondsky/claude-skills, 227 stars), 703 Technologies Fuzzing Testing (jabrena/plinth, 446 stars), API Designer (Jeffallan/claude-skills, 12k stars) and Old Coder API Design (AmazingAng/old-coder, 749 stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains API Contract Openapi?

makifbaysal (a GitHub user) maintains it in makifbaysal/tasktrooper, which has 109 GitHub stars. The repository holds 99 skills in this directory. The repository was last updated on October 7, 2026.

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