Runtime

Bindings

Give guest code narrow, validated host-backed commands.

Bindings expose narrow, validated host functions to executed code as VM-local commands. The handler stays in the trusted host and the guest receives only its JSON result.

import { binding, bindings } from "@rivet-dev/agentos";
import { JavaScriptRuntime } from "@rivet-dev/agentos/javascript";
import { z } from "zod";

const toolBindings = bindings({
	name: "tools",
	description: "Curated host capabilities for generated code.",
	bindings: {
		weather: binding({
			description: "Look up a city's temperature.",
			inputSchema: z.object({ city: z.string() }),
			execute: ({ city }) => ({
				city,
				tempF: city === "San Francisco" ? 61 : 75,
			}),
		}),
	},
});

const runtime = await JavaScriptRuntime.create({
	bindings: [toolBindings],
	permissions: { binding: "allow" },
});

Bindings are declared with binding() and bindings() from @rivet-dev/agentos, then passed through the normal AgentOsOptions accepted by either language runtime. See the general AgentOS Bindings docs for schemas, command naming, permissions, and handler behavior; see the Code Mode cookbook for the complete pattern.