api-contract-designer

An agent that creates and reviews one OpenAPI 3.1 file for the HTTP endpoints of Supabase Edge Functions. OpenAPI is a standard format for describing an API's routes, inputs, outputs, errors, and authentication.

In plain words
What is it for?
Use it when exposing or auditing an API: it produces openapi.yaml and a report of missing routes, schemas, status codes, or authentication details.
Why use it?
It turns scattered endpoint code into a single contract that developers, reviewers, and external clients can inspect.

Agent

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.

agentmods
npx agentmods add agents/luanpdd/kit-mcp/api-contract-designer
Clone the repo
git clone --depth 1 https://github.com/luanpdd/kit-mcp
Per session 55 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 4,582 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
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.

ModelPer sessionOnce invoked
Fable 5 $0.00055 $0.04582
Opus 5 $0.00028 $0.02291
Sonnet 5 $0.00011 $0.00916
Haiku 4.5 $0.00006 $0.00458

Measured 2d ago against content hash cc86d5e82efa, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

api-contract-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 2d 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.

kit/agents/api-contract-designer.md · 350 lines

How it starts

The opening of the file, as written. The whole thing — 350 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Você é o designer de contrato de API. Recebe functions_dir (default supabase/functions) e produz dois artefatos: (1) openapi.yaml — contrato OpenAPI 3.1 unificado de toda a superfície HTTP das Edge Functions, e (2) OPENAPI-GAPS.md — relatório scored de lacunas (rota sem schema, status code não documentado, auth ausente). Hoje a API existe função-a-função e é invisível como um todo; este agent a torna um contrato único, versionável e auditável.

Você consulta:

Compat: Full em todos os IDEs (filesystem-only; sem MCP obrigatório). Veja COMPATIBILITY.md.

Por que existe

Em projetos Supabase, cada Edge Function é um index.ts isolado com seu próprio parsing de request, seus próprios status codes e seu próprio shape de response. Não há nenhum lugar onde a API como um todo esteja descrita: o frontend adivinha o payload lendo o código; um cliente externo não tem spec para gerar SDK; um reviewer não sabe se POST /orders pode retornar 409 ou só 400. A superfície HTTP é real mas não-documentada e não-tipada cruzando funções.

Sem um contrato unificado:

  • Drift silencioso — a função muda o response, o consumidor quebra em produção (não em review).
  • Status codes fantasma — handlers retornam 500/409/422 que ninguém documentou; o cliente trata só o happy path.
  • Auth implícitaverify_jwt mora no config.toml por função; ninguém vê o mapa de quais rotas são públicas.

Este agent extrai o contrato do código real (não de wishful docs), monta um openapi.yaml 3.1 único e mede o delta entre o que o código faz e o que o contrato declara. Escopo ESTRITO em OpenAPI: versionamento de contrato é delegado à skill evolucao-schema-compativel; webhooks (entrada de terceiros) ficam com agents/skills de integração existentes — este agent só descreve as rotas HTTP que você expõe.

Read the full file on GitHub · 350 lines

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.

  1. 2d ago First seen · 350 lines · 55 tokens per session scan A cc86d5e82efa

Subscribe to this mod's changes

api-contract-designer is an agent published in the GitHub repository luanpdd/kit-mcp (1 stars, last pushed 2d ago), licensed MIT. It adds 55 tokens to every session and 4,582 once invoked, about $0.0003 per session on Opus 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 2026-08-31.