Crate onetool 

A sandboxed Lua REPL for LLM tool use.

LLM agents typically need dozens of specialized tools (calculator, date formatter, string manipulator, etc.). Each tool requires a round-trip to the provider and you pay for every token exchanged. onetool replaces them all with a single sandboxed Lua REPL — the LLM writes code instead of calling single-purpose tools.

Quick Start

use onetool::Repl;

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let repl = Repl::new()?;

    let outcome = repl.eval("return 1 + 1")?;

    match outcome.result {
        Ok(values) => println!("Result: {:?}", values),
        Err(error) => println!("Error: {}", error),
    }

    for line in outcome.output {
        print!("{}", line);
    }

    Ok(())
}

Framework Adapters

Ready-to-use adapters (each behind a feature flag of the same name):

Feature	Module	Framework
genai	genai	genai multi-provider client
mistralrs	mistralrs	mistral.rs local inference
rig	rig	rig-core modular framework
aisdk	aisdk	aisdk Vercel AI SDK port
mcp	mcp	MCP server via rmcp

Security

The Lua runtime is sandboxed with policy-based access control. Functions are categorized into three tiers: safe (no check), unsafe (wrapped, denied by default), and forbidden (removed entirely). See runtime::sandbox for the full security model and runtime::sandbox::DEFAULT_API_SPEC for the complete function list.

Extending the Runtime

Register custom Rust functions via Repl::with_runtime (post-init) or Repl::new_with (pre-built runtime). See their documentation for examples.

Key Types

• Repl — main interface for evaluating Lua code
• repl::EvalOutcome — result of a single evaluation (return values + captured output)
• ReplError — error type for REPL operations
• runtime — runtime creation, sandboxing, output capture, docs, and package paths
• tool_definition — tool name, description, and JSON schema for LLM integration

Re-exports

pub use repl::Repl;

pub use repl::ReplError;

Modules

repl

runtime

Runtime creation and sandboxing.

tool_definition

Tool definition metadata for LLM integration.