Type Alias FunctionDeclaration 

pub type FunctionDeclaration = ToolDefinition;

A tool definition describing a callable function.

This is a type alias for ToolDefinition from core types, maintaining backward compatibility with existing code that uses FunctionDeclaration.

Aliased Type

pub struct FunctionDeclaration {
    pub name: String,
    pub description: String,
    pub parameters: Option<Value>,
    pub defer_loading: bool,
}

Fields

name: String

Name of the function

description: String

Description of what the function does

parameters: Option<Value>

JSON Schema describing the function parameters

defer_loading: bool

Keep this tool’s schema out of the model’s context until the model looks it up.

A provider with on-demand tool loading (Anthropic’s tool search) still sends the definition, but loads it into context only when the model searches for it, so a wide catalogue stops costing its full width on every request. Every other provider ignores it and sends the tool as usual, so the same request falls back across providers unchanged.