Trait Tool

Source

pub trait Tool: Send + Sync {
    // Required methods
    fn name(&self) -> &str;
    fn description(&self) -> &str;
    fn parameters_schema(&self) -> Value;
    fn execute<'life0, 'life1, 'async_trait>(
        &'life0 self,
        params: Value,
        ctx: &'life1 ToolContext,
    ) -> Pin<Box<dyn Future<Output = Result<Value>> + Send + 'async_trait>>
       where Self: 'async_trait,
             'life0: 'async_trait,
             'life1: 'async_trait;

    // Provided method
    fn is_builtin(&self) -> bool { ... }
}

Expand description

A custom MCP tool that agents can discover and call.

Implement this trait to create a compiled Rust tool. Tools are registered at server startup and exposed via GET /tools/list for agent discovery and POST /tools/{name} for invocation.

§Lifecycle

The tool is registered via ToolRegistry::register.
name, description, and parameters_schema are called at startup for the tool list.
execute is called each time an agent invokes the tool.

§Example

use async_trait::async_trait;
use anyhow::Result;
use serde_json::{json, Value};
use context_harness::traits::{Tool, ToolContext};

pub struct HealthCheckTool;

#[async_trait]
impl Tool for HealthCheckTool {
    fn name(&self) -> &str { "health_check" }
    fn description(&self) -> &str { "Check connector health" }

    fn parameters_schema(&self) -> Value {
        json!({
            "type": "object",
            "properties": {},
            "required": []
        })
    }

    async fn execute(&self, _params: Value, ctx: &ToolContext) -> Result<Value> {
        let sources = ctx.sources()?;
        Ok(json!({ "sources": sources.len() }))
    }
}

Required Methods§

Source

fn name(&self) -> &str

Returns the tool’s name.

Used as the route path (POST /tools/{name}) and in GET /tools/list responses. Should be a lowercase identifier with underscores (e.g., "create_ticket").

Source