Euclid-MCP: A Model Context Protocol Server for Deterministic Logical Reasoning via Prolog

TL;DR - Euclid-MCP is an open-source MCP server that lets LLM agents delegate logical inference to SWI-Prolog. It improves reliability on large rule-based problems by returning deterministic answers, proof traces, and derivation logs.

• Introduces Euclid-IR, a readable, engine-agnostic representation for Horn-clause logic.
• Supports a translate-run-inspect-repair workflow through a compact MCP tool interface.
• In an IT security and compliance evaluation, LLMs hallucinated on larger knowledge bases while Euclid-MCP produced exact answers with lower latency and more compact outputs.
• Positions symbolic reasoning, rather than semantic RAG, as the appropriate mechanism for deterministic rule enforcement.