fastapi-architect

fastapi-architect is an agent for Claude Code from AratKruglik/claude-sdlc. It costs 103 tokens per session (1,613 once invoked), scanned A, original, MIT.

A coding agent for building the server side of FastAPI applications, a Python framework for web APIs. It handles routes, data validation, authentication, database model stubs, API documentation, and the contract that a frontend uses to call the API.

In plain words
What is it for?
Use it to implement FastAPI endpoints, request and response schemas, dependency injection, asynchronous handlers, OAuth2/JWT login, configuration, and OpenAPI documentation. It can also outline the API contract for a separate frontend agent.
Why use it?
It removes the need to repeatedly decide how common FastAPI backend pieces should be structured. It also helps keep the API and its frontend-facing data formats clearly defined.

Agent for Claude Code

Written for Claude Code: effort in frontmatter. Also seen: model in frontmatter.

Part of the fastapi-plugin plugin — 2 skills, 2 agents shipped together

Good fit Use it to implement FastAPI endpoints, request and response schemas, dependency injection, asynchronous handlers, OAuth2/JWT login, configuration, and OpenAPI documentation. It can also outline the API contract for a separate frontend agent.

Compare 6 agents from other repositories ↓
Install with agentmods
npx agentmods add agents/aratkruglik/claude-sdlc/fastapi-architect
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/AratKruglik/claude-sdlc

Made for: Claude Code.

Or install fastapi-plugin, the plugin that ships this one along with the rest of its 2 skills, 2 agents.

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.

agentmods badge for fastapi-architect

README.md
[![agentmods](https://agentmods.dev/badge/agents/aratkruglik/claude-sdlc/fastapi-architect.svg)](https://agentmods.dev/agents/aratkruglik/claude-sdlc/fastapi-architect)
Your own site
<a href="https://agentmods.dev/agents/aratkruglik/claude-sdlc/fastapi-architect"><img src="https://agentmods.dev/badge/agents/aratkruglik/claude-sdlc/fastapi-architect.svg" alt="Measured on agentmods" height="20"></a>
Per session 103 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 1,613 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.

ModelPer sessionOnce invoked
Fable 5.1 $0.00103 $0.01613
Opus 5 $0.00051 $0.00807
Sonnet 5 $0.00021 $0.00323
Haiku 4.5 $0.00010 $0.00161

Measured 8d ago against content hash 5dafa3659ba8, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-08, from the pricing page.

Security

Grade A, and why

fastapi-architect 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 8d 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.

plugins/fastapi-plugin/agents/fastapi-architect.md · 97 lines

How it starts

The opening of the file, as written. The whole thing — 97 lines — stays where its author put it; the contents beside it link to each section on GitHub.

FastAPI Architect

FastAPI backend implementer. You build the server side of features: APIRouter endpoint groups, Pydantic v2 schemas, dependency injection chains, async handlers, OAuth2/JWT authentication, OpenAPI metadata, SQLAlchemy ORM model stubs, and pydantic-settings configuration. For SPA projects you design and document the API contract — the endpoint shape and Pydantic schema your endpoints expose — so the frontend architect (vue-architect / react-architect) can implement the UI.

First: load sdlc:architect-conventions via the Skill tool — it defines the shared hard rules, code quality bar, workflow steps, and the report/compact-summary contract. Everything below is FastAPI-specific and applies on top.

Project context

The orchestrator's injection prompt (from fastapi-plugin/stack.md) supplies stack-specific guidance. Read and follow it. The summary:

Layer Convention
Routing APIRouter(prefix="/items", tags=["items"]) per feature; included in main app via app.include_router(router)
Schemas Pydantic v2 BaseModel with model_config = ConfigDict(from_attributes=True) for ORM mode
Request validation Pydantic models as request body; Query(), Path(), Header() for params; Annotated for field constraints
Response response_model= on each endpoint to filter output schema; JSONResponse only for custom status codes
Dependency injection Depends() for DB session, auth, pagination. Async AsyncSession yielded from get_db() dependency
SQLAlchemy models class User(Base): id: Mapped[int] = mapped_column(primary_key=True) — definition only, types finalized by alembic-specialist
Auth OAuth2PasswordBearer + JWT (python-jose or authlib). get_current_user dependency checks token
Settings pydantic-settings class Settings(BaseSettings) reading from env/.env
Async All I/O-bound handlers async def. DB calls via AsyncSession. No sync blocking in async context

Read the full file on GitHub · 97 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. 8d ago First seen · 97 lines · 103 tokens per session scan A 5dafa3659ba8

Subscribe to this mod's changes

fastapi-architect is an agent published in the GitHub repository AratKruglik/claude-sdlc (33 stars, last pushed 4d ago), licensed MIT. It adds 103 tokens to every session and 1,613 once invoked, about $0.0005 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 2026-08-30.

Related

Other agents, from other repositories

drf-api

Django REST Framework specialist. Use PROACTIVELY to build and shape JSON APIs in Django projects — serializers, viewsets, routers, permissions, authentication, pagination, throttling, and filtering. Serializers own field validation; views own permissions.

toffyui/ccteams · 54 tokens

hermes

Backend specialist — FastAPI, Python, async, TDD (RED→GREEN→REFACTOR), modern Python stdlib, obsolete lib detection. Calls apollo for discovery, sends to themis.

ils15/pantheon-legacy · 44 tokens

python-fastapi-guidelines

A reference guide for developing backends with FastAPI, a Python framework for building web APIs. It is intended to be used only when the user explicitly requests this agent.

Dannykkh/skill-olympus · 32 tokens

python-engineer

Hands-on Python 3.12+ engineer. Ships async-first, type-safe, tested code with uv, ruff, FastAPI and Pydantic. TRIGGER WHEN: planning a new Python project, designing architecture, making tech-stack decisions, or implementing features. DO NOT TRIGGER WHEN: the task is writing tests (use python-test-engineer) or…

acaprino/daodan · 87 tokens

fastapi-pro

Build high-performance async APIs with FastAPI, SQLAlchemy 2.0, and Pydantic V2. Master microservices, WebSockets, and modern Python async patterns. Use PROACTIVELY for FastAPI development, async optimization, or API architecture.

NOMARJ/sigil · 57 tokens

django-expert

Write expert Django code with optimized models, views, and templates. Handles complex queries, middleware, and RESTful APIs. Use proactively for Django optimizations, custom middleware, or REST API development.

0xfurai/claude-code-subagents · 43 tokens