python-backend

Development rules for Python backends built with FastAPI, a Python web framework. They cover security, type annotations, and pytest, a Python testing tool.

In plain words
What is it for?
Building or reviewing FastAPI services, adding Python type annotations, handling backend security, and writing tests with pytest.
Why use it?
They give coding agents consistent project guidance for common backend concerns. This can reduce mistakes in API code, types, security checks, and tests.

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/achaykovsky/cursor-usage-templates/python-backend
Clone the repo
git clone --depth 1 https://github.com/achaykovsky/Cursor-Usage-Templates
Per session 0 Nothing until a file matches its globs; then the whole rule loads.
When invoked 470 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin unknown 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 $0.00000 $0.00470
Opus 5 $0.00000 $0.00235
Sonnet 5 $0.00000 $0.00094
Haiku 4.5 $0.00000 $0.00047

Measured yesterday against content hash b8e770033b6b, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

python-backend 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 yesterday.

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.

templates/rules/python-backend.mdc · 46 lines

The source is not reproduced here

No licence file

A repository with no LICENSE is all rights reserved by default, so the body is not copied here. The metadata, the measurements and the link are.

Read it on GitHub

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. yesterday First seen · 46 lines · 0 tokens per session scan A b8e770033b6b

Subscribe to this mod's changes

python-backend is a cursor rule published in the GitHub repository achaykovsky/Cursor-Usage-Templates (5 stars, last pushed 1mo ago), with no licence file. It costs nothing until one of its globs matches a file; then it loads 470 tokens. 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.