fastapi-specific

A set of coding rules for backend projects built with FastAPI, a Python framework for creating web APIs. The rules cover project structure, Pydantic data models, dependency injection, errors, database access, logging, and API contracts.

In plain words
What is it for?
Building and maintaining FastAPI services, including API design, validation, database queries, application logs, audit logs, and documentation.
Why use it?
It gives an AI coding agent shared conventions for making changes that fit the project and handle common backend concerns consistently.

Cursor rule

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 rules/e-gov/cursor-prompts/fastapi-specific
Clone the repo
git clone --depth 1 https://github.com/e-gov/cursor-prompts
Per session 2,182 This file is loaded in full into every session.
When invoked 2,182 The same file — it is already loaded in full.
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 $0.02182 $0.02182
Opus 5 $0.01091 $0.01091
Sonnet 5 $0.00436 $0.00436
Haiku 4.5 $0.00218 $0.00218

Measured 2d ago against content hash 8a58e1c116c9, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

fastapi-specific 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.

rules/python-fastapi/fastapi-specific.mdc · 135 lines

How it starts

The opening of the file, as written. The whole thing — 135 lines — stays where its author put it; the contents beside it link to each section on GitHub.

FastAPI-Specific Standards

Rule stack (use in this order for new work)

  1. mdc:rules/common/security.mdc, mdc:rules/common/integration-standards.mdc, mdc:rules/common/component-technical-standards.mdc, mdc:rules/common/agent-memory.mdc — policy, integration shape, component constraints, project memory.
  2. This file — FastAPI/Pydantic layout, contract generation, errors, lifecycle.
  3. mdc:rules/python-fastapi/python-documentation-standards.mdc — lean docstrings (only non-obvious behavior); deslop-aligned defaults.
  4. mdc:rules/python-fastapi/sqlalchemy-data-access.mdc, mdc:rules/python-fastapi/application-logging.mdc, mdc:rules/python-fastapi/audit-logging.mdc — DB queries, structlog, AuditLogger.
  5. AGENTS.md — commands, triggers, repo layout.

Scope

  • This rule applies to FastAPI backend work in repositories that adopt these conventions.
  • Keep guidance practical, concise, and production-oriented.
  • Application logging, audit logging, and SQLAlchemy access: mdc:rules/python-fastapi/application-logging.mdc, mdc:rules/python-fastapi/audit-logging.mdc, mdc:rules/python-fastapi/sqlalchemy-data-access.mdc.

Common rules (do not contradict; language-agnostic policy lives here)

  • mdc:rules/common/security.mdc — input validation, auth/session/token rules, error messages, security logging expectations, dependency hygiene.
  • mdc:rules/common/integration-standards.mdc — REST resource design, HTTP methods/status codes, RFC 7807 errors, OpenAPI contract-first, pagination at the API, correlation/trace headers for integrations.
  • mdc:rules/common/component-technical-standards.mdc — UTF-8, layered architecture, Alembic migrations (not on every startup), stateless service, env-based config, integration tests, JSON logs with correlation (conceptually), graceful shutdown / long-running job patterns.
  • mdc:rules/common/agent-memory.mdc — read/update docs/agent-memory.md.

Read the full file on GitHub · 135 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 · 135 lines · 2,182 tokens per session scan A 8a58e1c116c9

Subscribe to this mod's changes

fastapi-specific is a cursor rule published in the GitHub repository e-gov/cursor-prompts (34 stars, last pushed 4mo ago), licensed MIT. It adds 2,182 tokens to every session, about $0.0109 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.