Overview

Strands Agents is a simple yet powerful SDK that takes a model-driven approach to building and running AI agents. The TypeScript SDK brings key features from the Python Strands framework to Node.js environments, enabling type-safe agent development for everything from simple assistants to complex workflows.

Key Features

• 🪶 Lightweight & Flexible: Simple agent loop that works seamlessly in Node.js and browser environments
• 🔒 Type-Safe Tools: Define tools easily using Zod schemas for robust input validation and type inference
• 📋 Structured Output: Get type-safe, validated responses from LLMs using Zod schemas with automatic retry on validation errors
• 🔌 Model Agnostic: First-class support for Amazon Bedrock and OpenAI, with extensible architecture for custom providers
• 🔗 Built-in MCP: Native support for Model Context Protocol (MCP) clients, enabling access to external tools and servers
• ⚡ Streaming Support: Real-time response streaming for better user experience
• 🎣 Extensible Hooks: Lifecycle hooks for monitoring and customizing agent behavior
• 💬 Conversation Management: Flexible strategies for managing conversation history and context windows
• 🤝 Multi-Agent Orchestration: Graph and Swarm patterns for coordinating multiple agents

Quick Start

Installation

Ensure you have Node.js 20+ installed, then:

npm install @strands-agents/sdk

Basic Usage

import { Agent } from '@strands-agents/sdk'

// Create agent (uses default Amazon Bedrock provider)
const agent = new Agent()

// Invoke
const result = await agent.invoke('What is the square root of 1764?')
console.log(result)

Note: For the default Amazon Bedrock model provider, you'll need AWS credentials configured and model access enabled for Claude 4.5 Sonnet in your region.

Core Concepts

Agents

The Agent class is the central orchestrator that manages the interaction loop between users, models, and tools.

import { Agent } from '@strands-agents/sdk'

const agent = new Agent({
  systemPrompt: 'You are a helpful assistant.',
})

Model Providers

Switch between model providers easily:

Amazon Bedrock (Default)

import { Agent, BedrockModel } from '@strands-agents/sdk'

const model = new BedrockModel({
  region: 'us-east-1',
  modelId: 'anthropic.claude-3-5-sonnet-20240620-v1:0',
  maxTokens: 4096,
  temperature: 0.7
})

const agent = new Agent({ model })

OpenAI

import { Agent } from '@strands-agents/sdk'
import { OpenAIModel } from '@strands-agents/sdk/openai'

// Automatically uses process.env.OPENAI_API_KEY and defaults to gpt-4o
const model = new OpenAIModel()

const agent = new Agent({ model })

Streaming Responses

Access responses as they are generated:

const agent = new Agent()

console.log('Agent response stream:')
for await (const event of agent.stream('Tell me a story about a brave toaster.')) {
  console.log('[Event]', event.type)
}

Tools

Tools enable agents to interact with external systems and perform actions. Create type-safe tools using Zod schemas:

import { Agent, tool } from '@strands-agents/sdk'
import { z } from 'zod'

const weatherTool = tool({
  name: 'get_weather',
  description: 'Get the current weather for a specific location.',
  inputSchema: z.object({
    location: z.string().describe('The city and state, e.g., San Francisco, CA'),
  }),
  callback: (input) => {
    // input is fully typed based on the Zod schema
    return `The weather in ${input.location} is 72°F and sunny.`
  },
})

const agent = new Agent({
  tools: [weatherTool],
})

await agent.invoke('What is the weather in San Francisco?')

Vended Tools: The SDK includes optional pre-built tools:

• Notebook Tool: Manage text-based notebooks for persistent note-taking
• File Editor Tool: Perform file system operations (read, write, edit files)
• HTTP Request Tool: Make HTTP requests to external APIs

Structured Output

Get type-safe, validated responses from LLMs by defining the expected output structure with Zod schemas. The agent automatically validates the LLM's response and retries on validation errors:

import { Agent } from '@strands-agents/sdk'
import { z } from 'zod'

const PersonSchema = z.object({
  name: z.string().describe('Name of the person'),
  age: z.number().describe('Age of the person'),
  occupation: z.string().describe('Occupation of the person')
})

// Configure structured output at the agent level
const agent = new Agent({ 
  structuredOutputSchema: PersonSchema 
})

const result = await agent.invoke('John Smith is a 30 year-old software engineer')

// result.structuredOutput is fully typed based on the schema
console.log(result.structuredOutput.name) // "John Smith"
console.log(result.structuredOutput.age)  // 30

Error handling: The agent automatically retries with validation feedback when the LLM provides invalid output. If validation ultimately fails, a StructuredOutputException is thrown:

import { StructuredOutputException } from '@strands-agents/sdk'

try {
  const result = await agent.invoke('Extract person info...')
  console.log(result.structuredOutput)
} catch (error) {
  if (error instanceof StructuredOutputException) {
    console.error('Validation failed:', error.message)
  }
}

MCP Integration

Seamlessly integrate Model Context Protocol (MCP) servers:

import { Agent, McpClient } from "@strands-agents/sdk";
import { StdioClientTransport } from "@modelcontextprotocol/sdk/client/stdio.js";

// Create a client for a local MCP server
const documentationTools = new McpClient({
  transport: new StdioClientTransport({
    command: "uvx",
    args: ["awslabs.aws-documentation-mcp-server@latest"],
  }),
});

const agent = new Agent({
  systemPrompt: "You are a helpful assistant using MCP tools.",
  tools: [documentationTools], // Pass the MCP client directly as a tool source
});

await agent.invoke("Use a random tool from the MCP server.");

await documentationTools.disconnect();

Multi-Agent Orchestration

Coordinate multiple agents using built-in orchestration patterns.

Graph — You define a deterministic execution plan. Agents run as nodes in a directed graph, with edges controlling execution order. Parallel execution is supported, and downstream nodes run once all dependencies complete.

import { Agent, BedrockModel, Graph } from '@strands-agents/sdk'

const model = new BedrockModel({ maxTokens: 1024 })

const researcher = new Agent({
  model,
  id: 'researcher',
  systemPrompt: 'Research the topic and provide key facts.',
})

const writer = new Agent({
  model,
  id: 'writer',
  systemPrompt: 'Rewrite the research into a polished paragraph.',
})

const graph = new Graph({
  nodes: [researcher, writer],
  edges: [['researcher', 'writer']],
})

const result = await graph.invoke('What is the largest ocean?')

Swarm — The agents decide the routing. Each agent chooses whether to hand off to another agent or produce a final response, making the execution path dynamic and model-driven.

import { Agent, BedrockModel, Swarm } from '@strands-agents/sdk'

const model = new BedrockModel({ maxTokens: 1024 })

const researcher = new Agent({
  model,
  id: 'researcher',
  description: 'Researches a topic and gathers key facts.',
  systemPrompt: 'Research the answer, then hand off to the writer.',
})

const writer = new Agent({
  model,
  id: 'writer',
  description: 'Writes a polished final answer.',
  systemPrompt: 'Write the final answer. Do not hand off.',
})

const swarm = new Swarm({
  nodes: [researcher, writer],
  start: 'researcher',
  maxSteps: 4,
})

const result = await swarm.invoke('What is the largest ocean?')

Both patterns support streaming via .stream() for real-time access to handoff and node execution events. See the examples directory for complete working samples.

Documentation

For detailed guidance, tutorials, and concept overviews, please visit:

• Official Documentation: Comprehensive guides and tutorials
• API Reference: Complete API documentation
• Examples: Sample applications
• Contributing Guide: Development setup and guidelines

Contributing ❤️

We welcome contributions! See our Contributing Guide for details on:

• Development setup and environment
• Testing and code quality standards
• Pull request process
• Code of Conduct
• Security issue reporting

License

This project is licensed under the Apache License 2.0 - see the LICENSE file for details.

Security

See CONTRIBUTING for more information on reporting security issues.

⚠️ Preview Status

Strands Agents is currently in public preview. During this period:

• APIs may change as we refine the SDK
• We welcome feedback and contributions