building-python-mcp-servers SKILL.md skillA
building-python-mcp-servers from kajisho5/ffmpeg-skill is an agent skill: a SKILL.md folder an AI agent loads when a task calls for it.
mdr add kajisho5/ffmpeg-skill/building-python-mcp-servers@git:20260906.24c1610Pins git:20260906.24c1610 in mdr.lock. Pin the fingerprint instead.
- Audit grade
- A, 17 of 17 checks passed
- Kind
- SKILL.md skill
- Repository
- kajisho5/ffmpeg-skill
- Path
.claude/skills/mcp-server-design/SKILL.md- Versions recorded
- 1
- Latest version
- git:20260906.24c1610, committed Sep 6, 2026
- Size
- 12,922 bytes
- Repository stars
- 2,026
- License
- MIT
Builds robust Python MCP (Model Context Protocol) servers with FastMCP — tool design, error contracts, event-loop-safe blocking work, subprocess/CLI wrapping, single-file vs packaged distribution, global-state-free testing, and prompt-injection awareness. Use when writing an MCP server, exposing a tool or CLI to an LLM client, debugging tool registration/packaging, or testing MCP tools.
Collected from public GitHub. Every version is saved exactly as it was and never changes. Install it at an exact version with the mdr tool, and every file is checked before it reaches your agent. The main file is checked against the SHA-256 fingerprint recorded here, and the others against the fingerprints GitHub keeps for its source commit. The automatic checks below grade the latest version, and the same checks always give the same file the same grade.
What the file says
# Building Python MCP Servers
MCP servers expose tools to an LLM client (Claude Desktop, Claude Code, etc.).
The LLM is the caller, so the failure modes differ from a normal library: errors
must be machine-readable, every input is untrusted, and a green test suite often
proves nothing about whether the tools actually work. This skill encodes the
patterns that recur when these go wrong.
## Quick Start (FastMCP)
```python
from mcp.server.fastmcp import FastMCP
mcp = FastMCP("my-server")
@mcp.tool()
def read_config(path: str) -> dict:
"""Read a config file. `path` must be absolute."""
p = Path(path)
if not p.is_absolute():
return {"error": "path must be absolute"}
if not p.exists():
return {"error": f"no such file: {path}"}
return {"data": p.read_text()}
if __name__ == "__main__":
mcp.run()
```
## Error Contract: return, don't raise — and stay consistent
An uncaught exception surfaces to the LLM as an opaque protocol error it can't
reason about. Return a structured result with a predictable shape instead, and
make callers check for it.
- **Pick one error shape and use it everywhere.** A dict with an `"error"` key is
…Read the whole file at its exact version.
How to install
mdr add kajisho5/ffmpeg-skill/building-python-mcp-servers@sha256:edafa832aa275ac8The line at the top of this page pins the label git:20260906.24c1610, which is what most people want. This one pins the sha256 fingerprint of the contents instead, so it survives a label being moved. Either way the exact version is written to mdr.lock, and mdr install downloads and checks those contents again, so it installs them exactly or stops with an error.
[](https://markdownregistry.com/a/art_mxbmk35wqehonuce)
5 badge image fetches in 30 days. What the badge shows.
Versions
The registry has recorded 1 version of this file, committed on Sep 6, 2026.
Audit of the latest version
- pass: Frontmatter block present
- pass: Frontmatter declares a name
- pass: Frontmatter declares a description
- pass: Size between 200 bytes and 200 KB (12922 bytes)
- pass: No zero-width or bidi control characters
- pass: No instruction hidden inside an HTML comment
- pass: No link to an exfiltration or paste host
- pass: No credential-shaped string
- pass: No instruction to send local credentials anywhere
- pass: No text hidden with inline styles
- pass: No prompt-injection phrasing
- pass: No curl or wget piped into a shell
- pass: No recursive delete of root, home or parent
- pass: No instruction to read or print local credentials
- pass: No base64 blob over 200 characters
- pass: No link to a raw IP address
- pass: No script tag
Source
kajisho5/ffmpeg-skill · 2,026 stars · license MIT · pushed 2026-10-20 · branch main
API
GET https://markdownregistry.com/api/v1/artifacts/art_mxbmk35wqehonuce GET https://markdownregistry.com/api/v1/resolve?ref=kajisho5/ffmpeg-skill/building-python-mcp-servers GET https://markdownregistry.com/api/v1/blob/edafa832aa275ac8c8b6dd782cbc3fd51965e28d2840c06366e100c6e5321cae
Your AI assistant does the legwork. You hear about the deals worth your word. Hand yours the standing instructions at modelranch.com and it joins the network that reads files like this one.
Guides: the SKILL.md format and its required fields · what to check before you install a skill · how to pin a skill to an exact version · where to find agent skills · keeping a team on the same skills · which agent file does what.