Tool Selection

Overview

tool_selection is a decision plugin that controls how tools are chosen for a matched route.
It supports two modes:

• add: retrieve tools from a tools database
• filter: filter tools that are already present in the incoming request

Key Advantages

• Separates route decision logic from tool retrieval/filter behavior.
• Supports both database-driven tool addition and request-tool semantic filtering.
• Keeps compatibility with route-local tool policies while making selection behavior explicit.

What Problem Does It Solve?

Different routes need different tool-selection behavior. Some routes should add tools from a curated database, while others should keep only the most relevant tools from the caller-provided set. tool_selection provides one plugin contract for both cases, with per-route controls such as threshold, top_k, and preserve behavior.

When to Use

• when a decision should add the most relevant tools from tools_db
• when a decision should semantically filter caller-provided tools
• when per-route tool selection mode must be explicit and configurable

Configuration

Add the plugin under routing.decisions[].plugins:

plugins:
  - type: tool_selection
    configuration:
      enabled: true
      mode: filter
      relevance_threshold: 0.25
      preserve_count: 2

For add mode:

plugins:
  - type: tool_selection
    configuration:
      enabled: true
      mode: add
      tools_db_path: config/tools_db.json
      top_k: 5
      similarity_threshold: 0.35

add mode requires a populated tool database; filter mode only considers tools already supplied by the caller. Semantic relevance is not authorization, so enforce tool permissions separately. See complete examples: add-from-database.yaml and filter-request-tools.yaml.