Warrant MCP Server

When a machine says something was allowed, can you check why - without trusting the machine that allowed it?. It runs locally over stdio via the published package.

People connecting this server to Claude, Cursor, VS Code, or another MCP client. The project is written in Python.

VERIFIED ACTIVE

LAST COMMIT 2026-08-23 · ★ 4 · #198 OF 848 MAINTAINED OTHER · VERIFIED 2026-08-25

MIT · Python servers · how we verify → /methodology

01 · Install Warrant

Claude Code

claude mcp add s0fractal-warrant -- uvx warrant-verify

Claude Desktop / Cursor / VS Code - add to config

{
  "mcpServers": {
    "s0fractal-warrant": {
      "command": "uvx",
      "args": [
        "warrant-verify"
      ]
    }
  }
}

Same JSON for Cursor. For VS Code, rename the top-level key from `mcpServers` to `servers`.

Using another client? Same JSON, different key

Claude Desktop · mcpServers

Cursor · mcpServers

VS Code · servers

Windsurf · mcpServers

Zed · context_servers

Cline · mcpServers

Roo Code · mcpServers

Continue · mcpServers

LibreChat · mcpServers

Gemini CLI · mcpServers

Codex CLI · mcp_servers

Full setup guides: every client.

02 · Evidence

Security posture

What to check before giving this server access to your agent - from the registry, GitHub, and our own probes. We don't score safety; we show what's verifiable.

runs as local process (stdio) - runs on your machine with your user's permissions

repo age created 2026-07-05 - young repo, little track record yet

license MIT - declared in the repository

pypi package warrant-verify - check the name against the project README before installing (PyPI has no namespace ownership)

registry namespace io.github.s0fractal is GitHub-verified and matches the repo owner

03 · What Warrant can do

Prose above is summarized from the project's README and registry record - no invented capabilities.

Latest releases

v0.9.0 · 2026-08-01

0.9.0 - the published package disagreed with the published pack · BREAKING for records with implausible timestamps; no real record is affected. · SPEC §2's integer domain is now ±(2^53−1) rather than int64, in all…

v0.8.0 · 2026-07-31

pip install warrant-verify now gives you the MCP server as a command: · pip install warrant-verify · claude mcp add warrant -- warrant-mcp-server --store .warrants · Until now the server lived in…

v0.7.1 · 2026-07-31

Two defects in the first thing a stranger sees, both in the conformance runner's report rather than its verdict. · A partial implementation was told it had failed. With zero wrong answers and 78 UNRUN - the state every…

04 · Who maintains Warrant

Warrant is maintained by s0fractal. It's the only MCP server we track from this author; the repo dates to Jul 2026.

05 · Facts

repository: github.com/s0fractal/warrant
website: https://github.com/s0fractal/warrant/tree/master/integrations/mcp-server
category: other - ranked #198 of 848 actively-maintained other servers as of 2026-08-25.
release cadence: 10+ releases in the last 90 days (latest 2026-08-01)
registry: io.github.s0fractal/warrant (active, first published 2026-07-31 · 3 versions)
packages: pypi:warrant-verify

06 · Warrant FAQ

What is Warrant?

When a machine says something was allowed, can you check why - without trusting the machine that allowed it?. It runs locally over stdio via the published package.

Is Warrant still maintained?

Yes - as of 2026-08-25, its last commit was 2026-08-23 and it shipped 10+ releases in the last 90 days. We re-verify nightly.

How do I install Warrant?

Run `uvx warrant-verify`. You can also paste the ready-made client config above.

Does Warrant run locally?

Yes - it's a stdio server: it runs on your machine (via uvx) with your user's permissions. Your data stays local unless the server itself calls external APIs.

07 · Alternatives to Warrant

Alternatives to Warrant

Maintained other servers if Warrant isn't the fit.

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