First Agent

View the complete sample on GitHub

Strands Agents is an open source SDK that takes a model-driven approach to building AI agents in just a few lines of code. This quickstart guide will walk you through creating your first agent in TypeScript using large language models to handle planning and tool usage autonomously.

Prerequisites

• Node.js 22 or later (the version @strands-agents/sdk supports; older versions print warnings)
• AWS credentials configured with access to Amazon Bedrock, and the model enabled in your region
• Basic understanding of TypeScript/JavaScript programming

What this agent does

This is the smallest useful Strands agent: one agent, one model, no tools. It shows the loop every Strands agent is built on.

1. You create an agent with a model (Claude Sonnet 4.6 on Amazon Bedrock) and a system prompt that sets its behaviour: “You are a helpful assistant that provides concise responses.”
2. You invoke it with a message: “Hello! Tell me a joke.”
3. Strands sends the conversation to the model and streams the reply back to your terminal as it is generated.

There are no tools yet, so the model answers directly. Later samples add tools, and the same agent.invoke() call then lets the model decide when to use them.

Creating Your First Agent

Feature	Description
Agent Structure	Single agent architecture

The example in src/firstAgent.ts demonstrates how to:

• Create a basic agent with the Claude Sonnet 4.6 model from Amazon Bedrock
• Configure the agent with a system prompt
• Invoke the agent with a message
• Stream the response to the console

Running the Example

cd typescript/01-learn/01-first-agent
npm install
npx tsx src/firstAgent.ts

To use a different Bedrock model or inference profile, set MODEL_ID:

MODEL_ID=us.anthropic.claude-haiku-4-5-20251001-v1:0 npx tsx src/firstAgent.ts

Expected output

The agent prints one short, friendly reply, and the command exits with status 0. The joke varies from run to run because the model generates it fresh each time.

$ npx tsx src/firstAgent.ts
Here's one:

Why don't scientists trust atoms?

**Because they make up everything!** 😄

Want to hear another one?

Check that it works

Check	Command	Expected
Runs end to end	npx tsx src/firstAgent.ts	One reply, printed once, then echo $? shows 0
Compiles	npm run build && npm start	Same reply from the compiled dist/firstAgent.js
Model override	MODEL_ID=us.anthropic.claude-haiku-4-5-20251001-v1:0 npx tsx src/firstAgent.ts	A reply from Claude Haiku 4.5

Troubleshooting

You see	Cause	Fix
ModelError: The security token included in the request is invalid. (exit 1)	Missing or expired AWS credentials	Run aws sts get-caller-identity; refresh your credentials or AWS_PROFILE
ModelError: The provided model identifier is invalid. (exit 1)	MODEL_ID is misspelled or not available in your region	Use a model ID or inference profile listed in the Bedrock console for your region
NodeVersionSupportWarning or EBADENGINE warnings	Node.js older than 22	Upgrade to Node.js 22 or later

Additional Resources

• Strands Agents Documentation