Extensions

Extensions are named capabilities that agents can call during a run. They are declared in AgentConfig.extensions.

interface ExtensionDefinition {
  environment?: "agent" | "app";
  name: string;
  description?: string;
  parameters?: JsonSchema;
  code?: string;
}

Runtime Extensions

Runtime extensions run inside the managed runtime.

await agent.updateConfig({
  extensions: [
    {
      environment: "agent",
      name: "format_markdown",
      description: "Format text as Markdown.",
      parameters: {
        type: "object",
        properties: {
          text: { type: "string" },
        },
        required: ["text"],
      },
      code: `
export default async function ({ text }) {
  return String(text).trim();
}
`,
    },
  ],
});

MCP

MCP server management exists at the runtime layer. A typed AgentClient wrapper is not part of the first stable server-side SDK surface yet, so prefer extensions and capabilities in public app code.