Getting it into your agent
It runs from inside its repository, so the clone comes first — what it calls does not travel with the file alone.
git clone --depth 1 https://github.com/ericrisco/rsc-harnessnpx agentmods add skills/ericrisco/rsc-harness/fastapiWrote 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.
[](https://agentmods.dev/skills/ericrisco/rsc-harness/fastapi)<a href="https://agentmods.dev/skills/ericrisco/rsc-harness/fastapi"><img src="https://agentmods.dev/badge/skills/ericrisco/rsc-harness/fastapi/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/ericrisco/rsc-harness/fastapi"><img src="https://agentmods.dev/badge/skills/ericrisco/rsc-harness/fastapi.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector warn
SkillSpector: 3 findings, up to high
These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →
- high Privilege Escalation · line 167 Code accesses credential files (SSH keys, AWS credentials, etc.). This could indicate credential theft attempts.Fix: Remove references to credential paths. Use environment variables or secrets managers. For docs, use placeholder paths (e.g., /path/to/config). Never load .env or token files in production code paths.
- high Privilege Escalation · line 151 Code accesses credential files (SSH keys, AWS credentials, etc.). This could indicate credential theft attempts.Fix: Remove references to credential paths. Use environment variables or secrets managers. For docs, use placeholder paths (e.g., /path/to/config). Never load .env or token files in production code paths.
- medium Excessive Agency · line 451 Skill enables autonomous high-impact decisions without human-in-the-loop verification. Critical operations (destructive commands, financial transactions, data deletion) should require explicit user confirmation.Fix: Add human-in-the-loop confirmation for destructive, irreversible, or high-impact operations. Never auto-execute commands that modify files, send data, or alter system state.
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 5.1 | $0.00094 | $0.04947 |
| Opus 5.5 | $0.00038 | $0.01979 |
| Sonnet 5.5 | $0.00019 | $0.00989 |
| Haiku 4.5 | $0.00009 | $0.00495 |
Grade A, and why
fastapi 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 1mo 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.
How it starts
The opening of the file, as written. The whole thing — 470 lines — stays where its author put it; the contents beside it link to each section on GitHub.
FastAPI & modern Python services
The single authoritative skill for building, reviewing, testing, securing and shipping an async FastAPI service on Python 3.12+. The mental model: the app is a thin async HTTP layer over typed dependencies, a service/repository core, and explicit DB sessions. Routes validate and delegate; they never own business logic, raw SQL, or secrets.
Pinned stack: Python 3.12+, FastAPI 0.136+, Starlette 1.0+ (FastAPI 0.136 requires it;
avoid <1.0.1, GHSA-86qp-5c8j-p5mr), Pydantic v2 (2.7+) + pydantic-settings 2.x,
SQLAlchemy 2.0 async, Alembic 1.13+, asyncpg 0.30 / psycopg 3, httpx 0.28+,
pytest 8 + pytest-asyncio 1.0+ (asyncio_mode=auto), ruff 0.7+, mypy 1.13+ strict,
uv 0.5+, uvicorn 0.32+ / gunicorn 23+ + uvicorn-worker 0.3+, PyJWT 2.10+, argon2-cffi 23+,
pip-audit 2.7+, PostgreSQL 16. (All lower bounds; install the latest in each line.)
⚠️ SDD new-feature gate — read this first. If this skill fired on a new, non-trivial feature or behaviour change and there is no approved spec + plan under
02-DOCS/wiki/sdd/, STOP — do not write feature code yet. Hand off to../specify/SKILL.mdfirst: it runs brainstorm → spec → plan → tasks before any code, then routes back here once the plan is approved. Build here directly only for a genuinely one-line / low-risk change. Method:../sdd/SKILL.md.
Out of scope, and where it goes instead: django for Django; Flask / sync WSGI,
notebooks and CLI-only scripts (no skill); language-level Python, typing and packaging →
python; framework-agnostic REST contracts — status codes, URL naming, versioning,
cursor vs offset → api-design (this skill covers their FastAPI implementation);
engine-level schema, indexing, EXPLAIN, zero-downtime migrations, PgBouncer →
postgresdb; language-agnostic injection / secret / authz theory →
secure-coding; Dockerfile, Compose and CI/CD mechanics →
deployment (this skill keeps only a Docker note).
What ships with it
7 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
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.
- 1mo ago First seen · 470 lines · 94 tokens per session scan A 38b5cc80928d
fastapi is a skill published in the GitHub repository ericrisco/rsc-harness (231 stars, last pushed yesterday), licensed MIT. It adds 94 tokens to every session and 4,947 once invoked, about $0.0004 per session on Opus 5.5. 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 2026-09-03.
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