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Tool Signatures

Each MCP tool has a signature consisting of: name, description, input schema, and safety metadata.

Signature Components​

MCP tool signature — product_search
{
  "name": "product_search",
  "description": "Search the product catalogue",
  "input_schema": {
    "type": "object",
    "properties": { "query": { "type": "string", "description": "Search query" } },
    "required": ["query"]
  },
  "metadata": {
    "action_type": "read",
    "risk_level": "none",
    "idempotent": true,
    "confirmation_required": false,
    "approval_required": false,
    "source_intent": "product.search",
    "source_entity": "product"
  }
}

The same action in a WebMCP tool definition carries inputSchema and annotations.axag instead of input_schema and metadata — the fields are the same. See Mapping Rules.

Naming Conventions​

  • Tool names MUST be unique within a tool registry
  • A tool's name is its intent with . replaced by _, so product.search becomes product_search — snake_case, entity_verb, and always traceable back to the annotation
  • Names are not configurable: to change a tool's name, change the intent