Mastra

Build typed TypeScript browser agents with Mastra's Model Router, registry, and Studio playground.

Mastra is a TypeScript framework that wraps the Vercel AI SDK with its own primitives: typed createTool definitions with input and output schemas, a top-level Mastra registry that wires agents into storage and observability, a Model Router that turns 'anthropic/claude-haiku-4-5' into a working client without a provider package install, and a built-in Studio playground (mastra dev) for chatting with your agents and replaying traces. The Steel integration runs each tool against a Steel cloud session, so the agent's tool surface is "drive a real browser" without leaving the Mastra primitives.

Requirements

  • Steel API Key: Active Steel subscription
  • Node.js: v22.13+
  • Packages: @mastra/core, steel-sdk, playwright, zod
  • Model provider key: Anthropic, OpenAI, Google, or any other provider supported by the Mastra Model Router

Connect Steel to Mastra

Define a createTool that opens a Steel session, register it on an Agent, and attach the agent to a top-level Mastra registry:

Typescript
import { Mastra } from "@mastra/core";

import { Agent } from "@mastra/core/agent";

import { createTool } from "@mastra/core/tools";

import { chromium } from "playwright";

import Steel from "steel-sdk";

import { z } from "zod";



const steel = new Steel({ steelAPIKey: process.env.STEEL_API_KEY! });



const openSession = createTool({

  id: "open-session",

  description: "Open a Steel cloud browser session.",

  inputSchema: z.object({}),

  outputSchema: z.object({

    sessionId: z.string(),

    liveViewUrl: z.string(),

  }),

  execute: async () => {

    const session = await steel.sessions.create({});

    const browser = await chromium.connectOverCDP(

      `${session.websocketUrl}&apiKey=${process.env.STEEL_API_KEY}`,

    );

    return { sessionId: session.id, liveViewUrl: session.sessionViewerUrl };

  },

});



const researchAgent = new Agent({

  id: "research-agent",

  name: "Steel Research",

  instructions: "You operate a Steel cloud browser via tools. ...",

  model: "anthropic/claude-haiku-4-5",

  tools: { openSession },

});



export const mastra = new Mastra({ agents: { researchAgent } });

Tools are passed as a record (not an array): the keys are what the model sees as tool names. With the registry wired up, npx mastra dev opens Studio at http://localhost:4111 so you can chat with research-agent and inspect its tool calls live.

Full runnable starter: Steel + Mastra recipe →

Resources

Contents

RequirementsConnect Steel to MastraResources