MCPserver.in

Public authority for MCP server discovery

MCP Tool

Definition

A tool is an executable action a server exposes. Clients discover tools via tools/list (returning name, description, inputSchema) and invoke them via tools/call with arguments matching the schema. Tools are the primary action surface of MCP.

Tool lifecycle

  1. Client sends tools/list → Server returns array of tool definitions
  2. Client sends tools/call with { name, arguments } → Server executes and returns content
  3. Tool may return text, images, or structured data

Security

Tools can mutate state. Prefer read-only tools for AI-agent callers. Treat tool permissions as a trust boundary.

Related terms