reductool 0.1.1

Allow Rust functions to be called by LLMs
Documentation

Reductool

This will let you turn Rust functions into LLM tools through an attribute macro. Here's a quick example

use reductool::aitool;

#[aitool]
/// Add allows you to add two numbers
fn add(a: i32, b: i32) -> i32 {
    a + b
}

Supported parameter types

The #[aitool] macro inspects function parameter types and emits a JSON Schema for each one. The following types are recognized specially; everything else falls back to "type": "string" in the schema and must implement serde::Deserialize to compile.

Rust type JSON Schema emitted Required? Notes
i8, i16, i32, i64, i128, isize, u8, u16, u32, u64, u128, usize { "type": "integer" } Yes, unless wrapped in Option
f32, f64 { "type": "number" } Yes, unless wrapped in Option
bool { "type": "boolean" } Yes, unless wrapped in Option
String { "type": "string" } Yes, unless wrapped in Option Prefer String over &str for deserialization.
[T; N] { "type": "array", "items": schema(T) } Yes, unless wrapped in Option At runtime, JSON must be an array of length exactly N; the schema does not encode this length constraint.
(T1, T2, ..., Tn) { "type": "array", "items": [schema(T1), …, schema(Tn)], "minItems": n, "maxItems": n } Yes, unless wrapped in Option Fixed-length, heterogeneous tuple.
Vec { "type": "array", "items": schema(T) } Yes, unless wrapped in Option If T is unrecognized, items default to { "type": "string" }.
Option schema(T) No (omitted from "required") Treated as optional; the schema does not add "null" type. Omit the field to pass None.
serde_json::Value (or a type named Value) {} Yes, unless wrapped in Option Accepts any JSON value. The detection also matches a bare Value ident.
Other path types (custom structs/enums, etc.) { "type": "string" } Yes, unless wrapped in Option Must implement serde::Deserialize to compile; schema may not reflect true shape.
&T (references) schema(T) — The schema normalizes &T to T, but the generated args struct uses the exact type; borrowed fields like &str generally cannot derive Deserialize here. Use owned types (e.g., String) instead.

Notes and constraints:

  • Parameters must be simple identifiers like arg: T. Patterns such as (_: T), (a, b): (T, U), or destructuring are rejected at compile time.
  • Methods with a receiver (e.g., self, &self) are not supported; annotate free functions only.
  • Required vs optional is determined solely by whether the type is Option<T>. All non-Option params are marked required.
  • The example in crates/reductool/examples/basic.rs demonstrates both a required-arg function (add(i32, i32)) and an optional-arg function (greet(Option<String>)).

License

Reductool Copyright (C) 2025 hadydotai

This program is free software: you can redistribute it and/or modify it under the terms of the GNU Affero General Public License as published by the Free Software Foundation, either version 3 of the License, or any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Affero General Public License for more details.

You should have received a copy of the GNU Affero General Public License along with this program. If not, see http://www.gnu.org/licenses/.