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 instructions/prefecthq/fastmcp/claude-mdgit clone --depth 1 https://github.com/PrefectHQ/fastmcpWhat 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 | $0.04780 | $0.04780 |
| Opus 5 | $0.02390 | $0.02390 |
| Sonnet 5 | $0.00956 | $0.00956 |
| Haiku 4.5 | $0.00478 | $0.00478 |
Grade A, and why
fastmcp CLAUDE.md 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 today.
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.
Copies of this mod
1 near-identical copy found in the catalogue:
- mcp-toolkit CLAUDE.md — 94% identical, 28 lines differ
How it starts
The opening of the file, as written. The whole thing — 211 lines — stays where its author put it; the contents beside it link to each section on GitHub.
FastMCP Development Guidelines
Audience: LLM-driven engineering agents and human developers
Note:
AGENTS.mdis a symlink to this file. EditCLAUDE.mddirectly.
FastMCP is a comprehensive Python framework (Python ≥3.10) for building Model Context Protocol (MCP) servers and clients. This is the actively maintained v2.0 providing a complete toolkit for the MCP ecosystem.
Required Development Workflow
CRITICAL: Always run these commands in sequence before committing.
uv sync # Install dependencies
uv run pytest -n auto # Run full test suite
In addition, you must pass static checks. This is generally done as a pre-commit hook with prek but you can run it manually with:
uv run prek run --all-files # Ruff + Prettier + ty
Tests must pass and lint/typing must be clean before committing.
Repository Structure
| Path | Purpose |
|---|---|
fastmcp_slim/fastmcp/ |
Library source code |
├─server/ |
Server implementation |
│ ├─auth/ |
Authentication providers |
│ └─middleware/ |
Error handling, logging, rate limiting |
├─client/ |
Client SDK |
│ └─auth/ |
Client authentication |
├─tools/ |
Tool definitions |
├─resources/ |
Resources and resource templates |
├─prompts/ |
Prompt templates |
├─cli/ |
CLI commands |
└─utilities/ |
Shared utilities |
tests/ |
Pytest suite |
docs/ |
Mintlify docs (gofastmcp.com) |
Core MCP Objects
When modifying MCP functionality, changes typically need to be applied across all object types:
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.
- today Changed · +2 tokens per session b039beb856f7
- yesterday First seen · 211 lines · 4,778 tokens per session scan A ec15d5c75a8a
fastmcp CLAUDE.md is an instructions file published in the GitHub repository PrefectHQ/fastmcp (27,470 stars, last pushed today), licensed Apache-2.0. It adds 4,780 tokens to every session, about $0.0239 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.
Other instructions, from other repositories
hypertool-mcp CLAUDE.md
Claude Code instructions for toolprint/hypertool-mcp, covering hypertool-mcp development instructions, for agents working on this project, 📋 essential reading, 🎯 high-level goal and 🏗️ agent instructions.
crewAI AGENTS.md
Instructions for crewAIInc/crewAI, covering agent instructions for crewai oss, key guidelines, message content and changing docs.
graphiti CLAUDE.md
Instructions for getzep/graphiti, covering claude.md, project overview, development commands, main development commands (run from project root) and install dependencies.
stagehand AGENTS.md
Instructions for browserbase/stagehand: Only a human may request changes to this file. Keep additions rare and limited to durable, repository-wide rules. -->.
graphiti AGENTS.md
Instructions for getzep/graphiti, covering repository guidelines, project structure & module organization, build, test, and development commands, coding style & naming conventions and testing guidelines.
autocontext CLAUDE.md
Instructions for greyhaven-ai/autocontext, covering claude.md, project overview, repository layout, commands and setup.