Agents API

The Agents API provides methods to interact with Mastra AI agents, including generating responses, streaming interactions, and managing agent tools.

Getting All Agents

Retrieve a list of all available agents:


const agents = await mastraClient.getAgents();

Working with a Specific Agent

Get an instance of a specific agent:


const agent = mastraClient.getAgent("agent-id");

Agent Methods

Get Agent Details

Retrieve detailed information about an agent:


const details = await agent.details();

Generate Response

Generate a response from the agent:


const response = await agent.generate({
  messages: [
    {
      role: "user",
      content: "Hello, how are you?",
    },
  ],
  threadId: "thread-1", // Optional: Thread ID for conversation context
  resourceId: "resource-1", // Optional: Resource ID
  output: {}, // Optional: Output configuration
});

Stream Response

Stream responses from the agent for real-time interactions:


const response = await agent.stream({
  messages: [
    {
      role: "user",
      content: "Tell me a story",
    },
  ],
});
 
// Process data stream with the processDataStream util
response.processDataStream({
  onChunk: async(chunk) => {
    console.log(chunk);
  },
});
 
 
// You can also read from response body directly
const reader = response.body.getReader();
while (true) {
  const { done, value } = await reader.read();
  if (done) break;
  console.log(new TextDecoder().decode(value));
}

Client tools

Client-side tools allow you to execute custom functions on the client side when the agent requests them.

Basic Usage


import { createTool } from '@mastra/client-js';
import { z } from 'zod';
 
const colorChangeTool = createTool({
  id: 'changeColor',
  description: 'Changes the background color',
  inputSchema: z.object({
    color: z.string(),
  }),
  execute: async ({ context }) => {
    document.body.style.backgroundColor = context.color;
    return { success: true };
  }
})
 
 
// Use with generate
const response = await agent.generate({
  messages: 'Change the background to blue',
  clientTools: {colorChangeTool},
});
 
// Use with stream
const response = await agent.stream({
  messages: 'Change the background to green',
  clientTools: {colorChangeTool},
});
 
response.processDataStream({
  onChunk: async (chunk) => {
    if (chunk.type === 'text-delta') {
      console.log(chunk.payload.text);
    } else if (chunk.type === 'tool-call') {
      console.log(`calling tool ${chunk.payload.toolName} with args ${JSON.stringify(chunk.payload.args, null, 2)}`);
    }
  },
});

Get Agent Tool

Retrieve information about a specific tool available to the agent:


const tool = await agent.getTool("tool-id");

Get Agent Evaluations

Get evaluation results for the agent:


// Get CI evaluations
const evals = await agent.evals();
 
// Get live evaluations
const liveEvals = await agent.liveEvals();

Stream

Stream responses using the enhanced API with improved method signatures. This method provides enhanced capabilities and format flexibility, with support for Mastra’s native format.


const response = await agent.stream(
  "Tell me a story",
  {
    threadId: "thread-1",
    clientTools: { colorChangeTool },
  }
);
 
// Process the stream
response.processDataStream({
  onChunk: async (chunk) => {
    if (chunk.type === 'text-delta') {
      console.log(chunk.payload.text);
    }
  },
});

AI SDK compatible format

To stream AI SDK-formatted parts on the client from an agent.stream(...) response, wrap response.processDataStream into a ReadableStream<ChunkType> and use toAISdkFormat:

client-ai-sdk-transform.ts


import { createUIMessageStream } from 'ai';
import { toAISdkFormat } from '@mastra/ai-sdk';
import type { ChunkType, MastraModelOutput } from '@mastra/core/stream';
 
const response = await agent.stream({ messages: 'Tell me a story' });
 
const chunkStream: ReadableStream<ChunkType> = new ReadableStream<ChunkType>({
  start(controller) {
    response.processDataStream({
      onChunk: async (chunk) => controller.enqueue(chunk as ChunkType),
    }).finally(() => controller.close());
  },
});
 
const uiMessageStream = createUIMessageStream({
  execute: async ({ writer }) => {
    for await (const part of toAISdkFormat(chunkStream as unknown as MastraModelOutput, { from: 'agent' })) {
      writer.write(part);
    }
  },
});
 
for await (const part of uiMessageStream) {
  console.log(part);
}

Generate

Generate a response using the enhanced API with improved method signatures and AI SDK v5 compatibility:


const response = await agent.generate(
  "Hello, how are you?",
  {
    threadId: "thread-1",
    resourceId: "resource-1",
  }
);