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When the ToolRouter is set to the search strategy, it hides your real MCP tools and instead exposes a small set of Meta-Tools. These tools follow the “Tool Search” pattern, allowing the LLM to autonomously find, inspect, and execute relevant capabilities from a massive catalog.

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The Meta-Tool Catalog

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mcp_search_tool_bm25

The entry point for discovery. The LLM calls this with a natural language query to find tools.
  • Input: query (string), limit (number).
  • Output: A list of tool names, descriptions, and the servers they belong to.
  • Usage: “I need to query a database” → returns sql_query, list_tables, etc.

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mcp_search_tool_regex

A precision tool for finding specific patterns in tool names or descriptions.
  • Input: query (Regex string), limit (number).
  • Output: Matching tools.
  • Usage: ^github_.* → returns all tools starting with “github_”.

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mcp_get_tool_schema

Load the technical details for a specific tool.
  • Input: toolName (string), serverName (optional string).
  • Output: The full JSON inputSchema for the requested tool.
  • Requirement: The LLM must call this after searching to know what arguments a tool accepts.

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mcp_execute_tool

The proxy executor for all discovered tools.
  • Input: toolName (string), args (object), serverName (optional string).
  • Output: The result of the actual MCP tool call.
  • Privacy: The SDK handles the routing to the correct MCP server automatically.

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The Discovery Lifecycle

The mcp-ts SDK implements the following flow to minimize context usage while maintaining capability:
1

Initial Injection

The SDK injects only the 4 Meta-Tools into the LLM context (cost: ~500 tokens).
2

Discovery (Search)

When the user asks for a specific capability, the LLM calls mcp_search_tool_bm25 or mcp_search_tool_regex.
3

Inspection (Get Schema)

Based on search results, the LLM calls mcp_get_tool_schema for the most relevant tool to see its parameters.
4

Execution

The LLM calls mcp_execute_tool with the constructed arguments. The SDK routes this call to the matching MCP server and returns the result.

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Why use Meta-Tools?

  1. Context Density: You can give an LLM access to 1,000 tools without using more than a few hundred tokens of “resting” context.
  2. Reduced Hallucinations: Because the LLM “finds” the tool definition right before using it, it is less likely to hallucinate parameters or use the wrong tool.
  3. Multi-Server Conflict Resolution: If two servers provide a tool named search, the Meta-Tools return the serverName as a namespace, allowing the LLM to specify which one to use.