FastMCP is a Python framework for building Model Context Protocol applications, which connect language models with tools and data through servers and clients. Developers use it to expose Python functions as tools, connect to local or remote MCP servers, and build interactive tool interfaces. The catalogue includes eight skills, three instructions, two rules, one setting, and one hook for FastMCP.
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.
git clone --depth 1 https://github.com/PrefectHQ/fastmcpWrote 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/rules/prefecthq/fastmcp/core-mcp-objects)<a href="https://agentmods.dev/rules/prefecthq/fastmcp/core-mcp-objects"><img src="https://agentmods.dev/badge/rules/prefecthq/fastmcp/core-mcp-objects/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/rules/prefecthq/fastmcp/core-mcp-objects"><img src="https://agentmods.dev/badge/rules/prefecthq/fastmcp/core-mcp-objects.svg" alt="Reviewed on agentmods" width="80" 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 5.1 | $0.00110 | $0.00110 |
| Opus 5.5 | $0.00044 | $0.00044 |
| Sonnet 5.5 | $0.00022 | $0.00022 |
| Haiku 4.5 | $0.00011 | $0.00011 |
Grade A, and why
core-mcp-objects 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.
What it actually says
There are four major MCP object types:
- Tools (src/tools/)
- Resources (src/resources/)
- Resource Templates (src/resources/)
- Prompts (src/prompts)
While these have slightly different semantics and implementations, in general changes that affect interactions with any one (like adding tags, importing, etc.) will need to be adopted, applied, and tested on all others. Note that while resources and resource templates are different objects, they are both in src/resources/.
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 · 13 lines · 110 tokens per session scan A 9e483173e3d6
core-mcp-objects is a cursor rule published in the GitHub repository PrefectHQ/fastmcp (28,090 stars, last pushed today), licensed Apache-2.0. It adds 110 tokens to every session, 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 2026-08-30.
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