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.
npx agentmods add skills/cookiemonsterdev/agents-skills/fastify-docsnpx skills add cookieMonsterDev/agents-skills --skill fastify-docsgit clone --depth 1 https://github.com/cookieMonsterDev/agents-skillsWrote 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/cookiemonsterdev/agents-skills/fastify-docs)<a href="https://agentmods.dev/skills/cookiemonsterdev/agents-skills/fastify-docs"><img src="https://agentmods.dev/badge/skills/cookiemonsterdev/agents-skills/fastify-docs.svg" alt="Measured on agentmods" height="20"></a>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 | $0.00089 | $0.01067 |
| Opus 5 | $0.00044 | $0.00534 |
| Sonnet 5 | $0.00018 | $0.00213 |
| Haiku 4.5 | $0.00009 | $0.00107 |
Grade A, and why
fastify-docs 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 3d 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 — 99 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Fastify questions are easy to answer from stale memory or Express-centric assumptions. Use this skill to ground answers in the official Fastify documentation and return the closest authoritative page instead of generic Node.js HTTP advice.
When to Use
Use this skill when the request is about:
- Fastify concepts, architecture, plugins, and encapsulation
- Server creation, configuration, routing, and the request lifecycle
- Request and reply objects, hooks, decorators, and error handling
- JSON Schema validation, serialization, and content-type parsing
- Plugins,
fastify-plugin, encapsulation scopes, and the@fastify/*ecosystem - Logging, middleware (Express-style), HTTP/2, and TypeScript support
- Testing with
inject(), serverless deployment, and production recommendations - Migration between Fastify major versions
Do not use this skill for:
- NestJS with the Fastify adapter unless the question is about underlying Fastify APIs. Use
nestjs-docsfor Nest abstractions. - Raw Express middleware patterns without Fastify context. Use
expressjs-docsinstead. - Third-party plugins not documented in the Fastify ecosystem guide unless the user needs general Fastify plugin patterns.
Workflow
1. Classify the request
Decide which bucket the question belongs to before searching:
- Getting started or introductory guides
- Core reference (server, routes, request, reply)
- Lifecycle, hooks, and plugins
- Validation, serialization, and parsers
- Logging, errors, and middleware
- TypeScript and production operations
- Ecosystem plugins and serverless
If you need a quick starting point, load references/topic-map.md and jump to the closest section.
2. Search official Fastify docs first
- Treat
fastify.dev/docs/latestas the source of truth for the current Fastify release. - Prefer pages under https://fastify.dev/docs/latest/.
- Search with the user's exact terms plus focused Fastify phrases such as
fastify.register,fastify-plugin,schema,preHandler, orreply.send. - When multiple pages are plausible, compare 2-3 candidate pages and pick the one that most directly answers the user's question.
- For version-specific breaking changes, check the migration guides before answering from older knowledge.
What ships with it
2 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.
- 3d ago First seen · 99 lines · 89 tokens per session scan A 2c5d0f7ec0bb
fastify-docs is a skill published in the GitHub repository cookieMonsterDev/agents-skills (4 stars, last pushed 14d ago), licensed MIT. It adds 89 tokens to every session and 1,067 once invoked, about $0.0004 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 2026-08-31.
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