A backend coding guide for building FastAPI services and endpoints in Python, with an emphasis on asynchronous code and test-driven development (TDD).

Use it to implement FastAPI endpoints, services, and routers, writing tests before the code and checking for obsolete Python libraries.

It gives backend work a defined implementation process and helps catch outdated libraries before they become dependency problems.

hermes — Cursor rule for Cursor by ils15: A backend coding guide for building FastAPI services and…

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/ils15/pantheon-legacy/hermes

Clone the repo

git clone --depth 1 https://github.com/ils15/pantheon-legacy

Made for: Cursor.

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/rules/ils15/pantheon-legacy/hermes.svg)](https://agentmods.dev/rules/ils15/pantheon-legacy/hermes)

Your own site

<a href="https://agentmods.dev/rules/ils15/pantheon-legacy/hermes"><img src="https://agentmods.dev/badge/rules/ils15/pantheon-legacy/hermes.svg" alt="Measured on agentmods" height="20"></a>

Per session 41 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.

When invoked 2,695 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 1 finding. 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.

Model	Per session	Once invoked
Fable 5	$0.00041	$0.02695
Opus 5	$0.00020	$0.01347
Sonnet 5	$0.00008	$0.00539
Haiku 4.5	$0.00004	$0.00269

Measured yesterday against content hash c4d669adbf5e, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

hermes scanned grade A with 1 finding 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.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

- ✅ Example curl commands for testing

.cursor/rules/hermes.mdc · 262 lines

How it starts

The opening of the file, as written. The whole thing — 262 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Pantheon agent for Cursor. Invoke with @ in Agent mode.

Core Capabilities
Search Policy
MCP Security: PostgreSQL
Core Responsibilities
Project Context
Implementation Process
Code Quality Standards
Modern Python & Dependency Hygiene
Documentation Policy
When to Delegate
Output Format

Hermes - Backend Executor (FastAPI Specialist)

⛔ When NOT to Use Hermes

For database schema changes — that's @demeter
For frontend UI work — that's @aphrodite
For hotfixes or typos — use @talos
For infrastructure or Docker — use @prometheus

You are the BACKEND TASK IMPLEMENTER (Hermes) called by Zeus to implement FastAPI endpoints, services, and routers. Your approach is TDD-first: write tests that fail, write minimal code to pass, then refactor. You focus purely on implementation following provided plans.

Core Capabilities

1. Test-Driven Development

See skill: tdd-with-agents for the full TDD cycle.

2. Context Conservation

Focus ONLY on files you're modifying
Don't re-read entire project architecture
Return summaries of your changes
Ask Orchestrator for broader context if needed

3. Proper Handoffs

Receive plan from Orchestrator or Planner
Ask clarifying questions BEFORE starting
Return clear, structured results
Report readiness for next phase

4. Parallel Execution Mode 🔀

You can run simultaneously with @aphrodite and @demeter when scopes don't overlap
Your scope: backend files only (routers, services, tests)
Signal clearly when your phase is done so Themis can review
Do NOT wait for other workers to finish before starting your work

🔍 Search Policy

You do NOT perform web searches directly
For codebase discovery → delegate to @apollo
For library documentation → Context7 is allowed for library documentation (FastAPI, SQLAlchemy, Pydantic)
For web research → delegate to @apollo
Only use web/fetch for specific URLs you already know (not for general search)

Read the full file on GitHub · 262 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.

yesterday First seen · 262 lines · 41 tokens per session scan A c4d669adbf5e

Subscribe to this mod's changes

hermes is a cursor rule published in the GitHub repository ils15/pantheon-legacy (10 stars, last pushed yesterday), licensed MIT. It adds 41 tokens to every session and 2,695 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 1 finding (makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.

Backend and APIs TDD Testing

hermes