Tool Trait

The base contract for any executable tool.

Every callable tool implements the Tool trait. A tool is a self-describing unit with a stable name, a human-readable description, a JSON Schema for its arguments, and an execute method.

The full file is src/tool.rs.

API

#[async_trait]
pub trait Tool: Send + Sync {
    fn name(&self) -> &str;
    fn description(&self) -> &str;
    fn parameters_schema(&self) -> serde_json::Value;
    async fn execute(&self, arguments: serde_json::Value) -> ToolResult<ToolOutput>;
    fn is_read_only(&self) -> bool { false }
    fn is_concurrency_safe(&self) -> bool { false }
    fn to_spec(&self) -> ToolSpec;
}

Spec

to_spec returns the ToolSpec that the model sees:

pub struct ToolSpec {
    pub name: String,
    pub description: String,
    pub parameters: serde_json::Value,  // JSON Schema
}

The spec is sent as part of every chat request when tools are available.

Markers

• is_read_only — true if the tool does not modify state. Read-only tools are eligible for parallel execution.
• is_concurrency_safe — true if the tool is safe to run concurrently with itself. False means the tool must run exclusively (one instance at a time across the whole runtime).

See also

• FunctionTool — the closure-backed impl.
• ToolRuntime — the runtime that executes tools.