What is api-designer?

An API design agent that defines how application endpoints work, including requests, responses, errors, authentication, headers, and cookies.

Use it to design REST routes, HTTP statuses, login and token flows, response formats, and database-field mappings.

It gives backend and frontend developers a shared description of the API before implementation begins.

api-designer — Agent for Claude Code by revfactory

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Clone the repo

git clone --depth 1 https://github.com/revfactory/harness-engineering-with-cc

Made for: Claude Code.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

README.md

[![agentmods](https://agentmods.dev/badge/agents/revfactory/harness-engineering-with-cc/api-designer/github.svg)](https://agentmods.dev/agents/revfactory/harness-engineering-with-cc/api-designer)

Your own site

<a href="https://agentmods.dev/agents/revfactory/harness-engineering-with-cc/api-designer"><img src="https://agentmods.dev/badge/agents/revfactory/harness-engineering-with-cc/api-designer/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

Your own site · 80×15

<a href="https://agentmods.dev/agents/revfactory/harness-engineering-with-cc/api-designer"><img src="https://agentmods.dev/badge/agents/revfactory/harness-engineering-with-cc/api-designer.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 73 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.

When invoked 477 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.

Origin original No closer match found in the catalogue.

Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

Model	Per session	Once invoked
Fable 5.1	$0.00073	$0.00477
Opus 5.5	$0.00029	$0.00191
Sonnet 5.5	$0.00015	$0.00095
Haiku 4.5	$0.00007	$0.00048

Measured 2mo ago against content hash 904092b8a0ca, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

api-designer scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2mo ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

ex-12-03-team-8-agents/.claude/agents/api-designer.md · 38 lines

What it actually says

역할

API 표면(엔드포인트 목록·메서드·요청/응답 스키마·에러 응답·헤더·쿠키)을 단일 마크다운으로 정의.
ui-designer에게 응답 구조 사전 공유 (훅 작성 입력).
db-migrator에게 컬럼 ↔ 필드 정렬 요청.
인증 흐름(JWT + refresh 발급/회전/검증) 명세.

입력

00_requirements.json (Phase 0 PM 산출물).
ui-designer로부터의 폼 에러 포맷 요청.
db-migrator로부터의 컬럼명·제약 알림.

절차

요구사항의 backend 카테고리 추출.
4 엔드포인트 초안 작성 (예: register / login / logout / ~~social~~).
ui-designer에게 로그인 성공 응답에 { user, accessToken }. refreshToken은 HttpOnly 쿠키. SendMessage.
db-migrator에게 users.email UNIQUE 제약. 실패 시 409로 매핑. SendMessage.
ui-designer / db-migrator로부터 회신 받아 응답·에러·제약 조정.
_workspace/features/{name}/01_api_design.md 작성 (섹션 1·2·3·4·5).

출력

_workspace/features/{name}/01_api_design.md

에러 핸들링

ui-designer ↔ db-migrator와 합의 사이클이 3회 이상 발생하면 PM에게 [BLOCKER.] 보고.
Edit 도구 미보유 — 구현 단계(Phase 2)에서 수정은 backend-impl에 위임.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

2mo ago First seen · 38 lines · 73 tokens per session scan A 904092b8a0ca

Subscribe to this mod's changes

api-designer is an agent published in the GitHub repository revfactory/harness-engineering-with-cc (123 stars, last pushed 5mo ago), licensed Apache-2.0. It adds 73 tokens to every session and 477 once invoked, about $0.0003 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

Backend and APIs

api-designer next to 6 agents from other repositories
Mod	Type	Stars	Last push	Licence	Scan	Tokens	Works with
api-designerrevfactory/harness-engineering-with-cc	Agent	123	5mo ago	Apache-2.0	A	73	Claude Code
php-developerdavepoon/buildwithclaude	Agent	3.7k	yesterday	MIT	A	51	Claude Code
backend-reviewerjeremylongshore/tons-of-skills-marketplace	Agent	2.9k	today	MIT	A	36	Claude Code
integrations-engineeravelikiy/great_cto	Agent	112	yesterday	MIT	A	106	Claude Code
gatetonone-ai/tonone	Agent	77	23d ago	MIT	A	19	Claude Code
broadcasting-agentSofttor/nestjs-hexagonal	Agent	5	1mo ago	MIT	A	58	Claude Code
dotnet-architecture-reviewerStefanTheCode/dotnet-ai-toolkit	Agent	26	3mo ago	MIT	A	102	Claude Code