Dev builds harness-router: MCP tool routing with Jev and Monte Carlo Tree Search

Revolutionary_Sir140 · reddit · 2026-09-26

A Reddit developer open-sourced harness-router, a lightweight router for MCP tools that avoids sending every tool definition to the LLM. It uses Jev for fast tool selection and Monte Carlo Tree Search for harder multi-step decisions, with MCP as the tool interface and confidence-based fallback when routing is uncertain. The goal is fewer tokens and faster tool selection for coding and agent harnesses. A demo and docs are live, and the author is building MCP benchmarks comparing standard LLM tool calling versus routed decisions, soliciting feedback from MCP agent builders.

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