Kitsune MCP

🦊 Kitsune MCP Let your agent test the MCP server it's building.

Edit a tool, reload("dev") , call it again. No client restart. ⭐ Saved you a restart? Star it on GitHub so others find it. 📖 Documentation · Hot-reload tutorial · Tools reference

AI agents installing this server (Cline, Claude Code, Cursor, …): follow llms-install.md. No clone or build needed. Add the uvx kitsune-mcp entry to your MCP settings.

One prompt: Claude finds the bug, fixes it, reloads, checks again. Real recording, 31 s.

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Why

Your agent edits an MCP tool, but the client still runs the old process. Someone has to restart it before the agent can test the fix.

With Kitsune, connect, call and reload are tools. The agent runs the whole loop itself:

connect("uv run my-mcp-server", name="dev")  # start your server

shapeshift("dev") # its tools appear in the client call("summarize", arguments={"url": "https://example.com"})

… the agent (or you) edits the tool …

reload("dev") # restart on fresh code, remount call("summarize", arguments={"url": "https://example.com"}) # new code, same session

No Docker needed: connect() runs your own server as a plain local process, so the loop stays fast.

It also mounts any of 130,000+ servers from 7 registries mid-session. If Docker is installed, community packages run caged.

Try it: hot-reload tutorial · examples/demo-hot-reload/

Install

Claude Code

claude mcp add -s user kitsune -- uvx kitsune-mcp

Any other client (Claude Desktop, Cursor, Windsurf, Cline, Zed, …):

{

"mcpServers": { "kitsune": { "command": "uvx", "args": ["kitsune-mcp"] } } }

Also on PyPI (pip install kitsune-mcp, then "command": "kitsune-mcp") and npm (npx kitsune-mcp, delegates to uvx).

Requirements: Python 3.12+ · uv · node/npx for npm-based servers · Docker optional: not used for hot-reload, only to cage community servers when installed.

Three things it does

Borrow a server you never configured

search("web scraping")

shapeshift("firecrawl", tools=["scrape_url"]) # mount one tool, not the whole server call("scrape_url", arguments={"url": "https://example.com"}) shapeshift() # drop it, session stays up

Try a community package, caged

search("pdf", registry="glama")

shapeshift("mcp-pdf-tools", confirm=True) # npm/PyPI run in hardened Docker when available call("extract_text", arguments={"path": "report.pdf"}) shapeshift()

Add credentials mid-session

auth("BRAVE_API_KEY", "sk-...")  # saved to ~/.kitsune/.env, no restart

shapeshift("brave", tools=["brave_web_search"])

Full live walkthrough: docs/demo-realtime.md.

When to use it, when not to

How it works

shapeshift(server_id) picks a transport (stdio, HTTP+SSE, WebSocket, Docker), connects, reads tools/list, and registers each tool as a native tool with the server's real schema. The client receives notifications/tools/list_changed and sees first-class tools, with no wrapper in between. shapeshift() with no argument removes them and closes the connection.

search() covers the official servers repo, the MCP Registry, Glama, npm, PyPI, GitHub (github:owner/repo) and Smithery (hosted servers, free API key).

Tools

Default profile: 9 tools. Standing cost: ~1,774 tokens/turn on clients that load every tool schema up front (measured with python examples/benchmark.py); ~70 tokens/turn on Claude Code with Tool Search, where schemas load only on first use (measured on Claude Code 2.1.319, 2026-11-06).

KITSUNE_TOOLS=all (or the kitsune-forge command) adds developer tools: inspect (schemas, credential check, token cost), test (quality score 0–100), bench (p50/p95 latency), compare, prewarm, craft, setup, and more. See docs/tools.md. Companion skills for Claude Code: kitsune-dev, kitsune-improve.

Safety, in short

• Community sources need consent. npm, PyPI and GitHub servers require confirm=True. The model can set that flag itself, so real approval belongs in your client's tool-approval UI.
• `connect()` runs the command it is given, as your user, with no consent gate and no cage. It is meant for your own code. Approve connect calls in your client before the agent runs them.
• Community packages run in a Docker cage by default when Docker is installed: no host filesystem, --cap-drop ALL, read-only root, memory and PID limits. Credentials are passed by name, never in argv.
• Version pins (TOFU). A later malicious publish doesn't silently replace a version you already ran.
• Opt-in action guard. A ~/.kitsune/policy.json checks every downstream call against allow/ask/deny rules, path roots and a host allowlist. ask goes to you through MCP elicitation.
• Install commands are validated and launched without a shell. fetch() blocks private hosts and re-checks every redirect.

Don't run it unattended with production admin, billing or security credentials. The full model, including what it does not protect against: docs/safety.md.

More

• Configuration: env and .env lookup, tool profiles, sandbox and trust settings, Smithery, GATEWAY, mount patterns
• Performance: cold/warm latency and token cost compared with always-on servers
• Transports · Compatibility · Agent patterns · Worked scenarios

Why "Kitsune"?

In Japanese folklore the kitsune (狐) is known for what it can *become*: it borrows a form, uses that power, casts it off and returns to itself. That is the product loop.

*I am not Japanese, and I use this name with the highest respect for the mythology and culture it comes from. The parallel felt too precise to ignore.*

Contributing

make dev     # install with dev dependencies

make test # pytest make lint # ruff

Issues and PRs welcome: github.com/kaiser-data/kitsune-mcp · CHANGELOG.md

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*MIT License · Python 3.12+ · Built on FastMCP*