agnt-macros

Proc-macros for the agnt agent runtime. Currently provides one attribute: #[tool].

use agnt_macros::tool;
use serde::{Deserialize, Serialize};

#[derive(Deserialize)]
struct AddArgs { a: i64, b: i64 }
#[derive(Serialize)]
struct AddOut { sum: i64 }

/// Add two integers and return their sum.
#[tool]
fn add(args: AddArgs) -> Result<AddOut, String> {
    Ok(AddOut { sum: args.a + args.b })
}

// Generates:
//   pub struct Add;
//   impl agnt_core::TypedTool for Add { const NAME = "add"; ... }

The first-line doc comment becomes the tool description. The PascalCase struct name is derived from the snake_case fn name. The generated impl forwards to the original function, which is left in place so you can still call it directly from Rust.

⚠️ v0.3.x limitation

The generated schema() returns a bare {"type": "object"} with no field metadata — the model cannot see your argument names or types from the schema alone and must infer them from the description. For any non-trivial tool, hand-writing a TypedTool impl where you control schema() is currently still better UX.

Real JSON Schema derivation (via schemars) is planned for v0.4 behind an opt-in #[tool(schema = schemars)] attribute.

Requirements

• Exactly one argument whose type becomes TypedTool::Args
• Return type must be Result<Output, Error>
• A doc comment is strongly recommended (becomes the description)

See the flagship agnt crate for the agent runtime this plugs into, or the repository for the broader project.

License

Dual-licensed under MIT OR Apache-2.0.