Prolog Reasoner MCP Server

SWI-Prolog as a "logic calculator" for LLMs - available as an MCP server and a Python library. Eliminate the black box from LLM logical reasoning. Its 4 documented tools cluster into prolog, read & search, rule, max. It runs locally over stdio via the published package.

People who work with logic programming, prolog and reasoning and want it reachable from Claude, Cursor, VS Code, or another MCP client. The project is written in Python.

VERIFIED ACTIVE

LAST COMMIT 2026-05-01 · ★ 11 · #724 OF 945 MAINTAINED OTHER · VERIFIED 2026-09-18

MIT · Python servers · how we verify → /methodology

01 · Install Prolog Reasoner

before you install - you'll need

Set PROLOG_REASONER_LLM_API_KEY before connecting.

Claude Code

claude mcp add rikarazome-prolog-reasoner -- uvx prolog-reasoner

Claude Desktop / Cursor / VS Code - add to config

{
  "mcpServers": {
    "rikarazome-prolog-reasoner": {
      "command": "uvx",
      "args": [
        "prolog-reasoner"
      ]
    }
  }
}

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

license MIT - declared in the repository

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

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

03 · What Prolog Reasoner can do

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

What you can build

An agent gets 4 documented tools across prolog, read & search, rule, including prolog_code, query, rule_bases, max_results.

Capability map

Tools grouped from the project's README - what Prolog Reasoner lets an agent do.

Prolog

1 tool - e.g. Prolog facts and rules (string)

prolog_code

read & search

1 tool - e.g. Prolog query to run, e.g. "mortal(X)" (string)

query

Rule

1 tool - e.g. optional list of saved rule base names to prepend to prolog_code (in order). Use this to reuse stable domain rules across calls without re-sending them

rule_bases

Max

1 tool - e.g. cap the number of solutions returned (default 100)

max_results

Latest releases

v0.2.0 · 2026-04-16

Added · Rule bases · Named, reusable Prolog modules stored as .pl files under PROLOG_REASONER_RULES_DIR (default ~/.prolog-reasoner/rules/). Four new MCP tools - save_rule_base, list_rule_bases, get_rule_base…

v0.1.0 · 2026-04-14

Initial public release of prolog-reasoner - SWI-Prolog as a "logic calculator" for LLMs, available as both an MCP server and a Python library. · Added · MCP server exposing a single tool, execute_prolog, for use by…

04 · Who maintains Prolog Reasoner

Prolog Reasoner is maintained by rikarazome. It's the only MCP server we track from this author; the repo dates to Apr 2026.

05 · Facts

repository
github.com/rikarazome/prolog-reasoner
category
other - ranked #724 of 945 actively-maintained other servers as of 2026-09-18.
registry
io.github.rikarazome/prolog-reasoner (active, first published 2026-04-17)
packages
pypi:prolog-reasoner

06 · Prolog Reasoner FAQ

Is Prolog Reasoner still maintained?

Yes - as of 2026-09-18, its last commit was 2026-05-01. We re-verify nightly.

What can Prolog Reasoner do?

An agent gets 4 documented tools across prolog, read & search, rule, including prolog_code, query, rule_bases, max_results.

How do I install Prolog Reasoner?

Run `uvx prolog-reasoner`. The README documents one environment variable (PROLOG_REASONER_LLM_API_KEY) to set first. Set PROLOG_REASONER_LLM_API_KEY before connecting. You can also paste the ready-made client config above.

Does Prolog Reasoner 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 Prolog Reasoner

Alternatives to Prolog Reasoner

Maintained other servers if Prolog Reasoner isn't the fit.

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