# 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:

```typescript
const agents = await mastraClient.listAgents()
```

Returns a record of agent IDs to their serialized agent configurations.

## Working with a specific agent

Get an instance of a specific agent by its ID:

```typescript
export const myAgent = new Agent({
  id: 'my-agent',
})
```

```typescript
const agent = mastraClient.getAgent('my-agent')
```

## Agent methods

### `details()`

Retrieve detailed information about an agent:

```typescript
const details = await agent.details()
```

### `generate()`

Generate a response from the agent:

```typescript
const response = await agent.generate(
  [
    {
      role: 'user',
      content: 'Hello, how are you?',
    },
  ],
  {
    memory: {
      thread: 'thread-abc', // Optional: Thread ID for conversation context
      resource: 'user-123', // Optional: Resource ID
    },
    structuredOutput: {}, // Optional: Structured Output configuration
  },
)
```

You can also use the simplified string format with memory options:

```typescript
const response = await agent.generate('Hello, how are you?', {
  memory: {
    thread: 'thread-1',
    resource: 'resource-1',
  },
})
```

### `stream()`

Stream responses from the agent for real-time interactions:

```typescript
const response = await agent.stream('Tell me a story')

// Process data stream with the processDataStream util
response.processDataStream({
  onChunk: async chunk => {
    console.log(chunk)
  },
})
```

You can also use the simplified string format with memory options:

```typescript
const response = await agent.stream('Tell me a story', {
  memory: {
    thread: 'thread-1',
    resource: 'resource-1',
  },
  clientTools: { colorChangeTool },
})

response.processDataStream({
  onChunk: async chunk => {
    if (chunk.type === 'text-delta') {
      console.log(chunk.payload.text)
    }
  },
})
```

You can also read from response body directly:

```typescript
const reader = response.body.getReader()
while (true) {
  const { done, value } = await reader.read()
  if (done) break
  console.log(new TextDecoder().decode(value))
}
```

#### 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 `toAISdkStream`:

```typescript
import { createUIMessageStream } from 'ai'
import { toAISdkStream } from '@mastra/ai-sdk'
import type { ChunkType, MastraModelOutput } from '@mastra/core/stream'

const response = await agent.stream('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 toAISdkStream(chunkStream as unknown as MastraModelOutput, {
      from: 'agent',
    })) {
      writer.write(part)
    }
  },
})

for await (const part of uiMessageStream) {
  console.log(part)
}
```

### `sendSignal()`

Send a signal to an active agent run or memory thread. Use this with `subscribeToThread()` so the client can render the stream that wakes from, or receives, the signal.

```typescript
const agent = mastraClient.getAgent('support-agent')

const result = await agent.sendSignal({
  signal: {
    type: 'user-message',
    contents: 'Also consider the customer note I just added.',
  },
  resourceId: 'user-123',
  threadId: 'thread-abc',
})

console.log(result.runId)
```

Use `ifActive.behavior` and `ifIdle.behavior` to control whether Mastra delivers, persists, discards, or wakes from a signal:

```typescript
await agent.sendSignal({
  signal: { type: 'user-message', contents: 'Store this for later.' },
  resourceId: 'user-123',
  threadId: 'thread-abc',
  ifIdle: {
    behavior: 'persist',
  },
})
```

Pass `ifIdle.streamOptions` when the idle wake-up stream needs options such as model settings, tools, or runtime context:

```typescript
await agent.sendSignal({
  signal: { type: 'user-message', contents: 'Start from this signal.' },
  resourceId: 'user-123',
  threadId: 'thread-abc',
  ifIdle: {
    behavior: 'wake',
    streamOptions: {
      maxSteps: 3,
    },
  },
})
```

Returns `{ accepted: true, runId: string }`.

**signal** (`{ type: 'user-message' | 'system-reminder' | string; contents: string | Array<TextPart | FilePart>; attributes?: Record<string, JSONValue>; metadata?: Record<string, unknown>; providerOptions?: ProviderMetadata }`): \`user-message\` signals without attributes are treated as plain user input. All other signals — including \`user-message\` with \`attributes\`, \`system-reminder\`, and custom types — are wrapped in an XML element named after the signal type with \`attributes\` rendered as XML attributes (e.g. \`\<user name="Devin" from="slack">message\</user>\`). The model sees the XML; the UI sees the raw contents and can read \`attributes\` for custom rendering. \`providerOptions\` is attached to the resulting prompt turn and persisted on the stored signal message.

**runId** (`string`): Run ID to target directly.

**resourceId** (`string`): Resource ID for the memory thread. Use with \`threadId\` for thread-targeted signals.

**threadId** (`string`): Thread ID to target. Use with \`resourceId\` for thread-targeted signals.

**ifActive.behavior** (`'deliver' | 'persist' | 'discard'`): Controls what happens when the target thread is active. Defaults to \`deliver\`.

**ifIdle.behavior** (`'wake' | 'persist' | 'discard'`): Controls what happens when the target thread is idle. Defaults to \`wake\`.

**ifIdle.streamOptions** (`Omit<AgentExecutionOptions, 'messages'>`): Options for the stream that starts when \`ifIdle.behavior\` is \`wake\`.

### `subscribeToThread()`

Subscribe to raw stream chunks for a memory thread. Use this to render output from a thread that may be started or continued by `sendSignal()`.

```typescript
const agent = mastraClient.getAgent('support-agent')

const subscription = await agent.subscribeToThread({
  resourceId: 'user-123',
  threadId: 'thread-abc',
})

await subscription.processDataStream({
  onChunk: chunk => {
    console.log(chunk)
  },
  reconnect: true,
})
```

`subscribeToThread()` returns the underlying `Response` plus a `processDataStream()` helper. The helper reads the subscription stream until the connection closes or the request is aborted. Pass `reconnect: true` to resubscribe when the transport closes or a reconnect request fails, such as after a proxy idle timeout.

**resourceId** (`string`): Resource ID for the memory thread.

**threadId** (`string`): Thread ID to subscribe to.

**processDataStream().reconnect** (`boolean | { maxRetries?: number; delayMs?: number }`): Reconnects the subscription stream after it closes or a reconnect request fails. \`true\` retries indefinitely with a one-second delay.

### `streamUntilIdle()`

Stream a response and keep the stream open until every [background task](https://mastra.ai/docs/agents/background-tasks) dispatched during the run completes. The server re-enters the agentic loop on each task completion so the LLM can react to results in the same call. Requires background tasks to be [enabled on the Mastra instance](https://mastra.ai/reference/configuration) and a memory thread; otherwise the call falls through to a plain `stream()`.

```typescript
const response = await agent.streamUntilIdle('Research solana for me', {
  memory: {
    thread: 'thread-1',
    resource: 'resource-1',
  },
  maxIdleMs: 5 * 60_000, //optional
})

response.processDataStream({
  onChunk: async chunk => {
    if (chunk.type === 'background-task-completed') {
      console.log('task complete:', chunk.payload.taskId)
    }
  },
})
```

### `resumeStreamUntilIdle()`

Resume a suspended agent stream with custom data and keep the stream open until every [background task](https://mastra.ai/docs/agents/background-tasks) dispatched during the run completes. Use this to continue execution after a suspension point, such as a workflow suspend within an agent. Requires background tasks to be [enabled on the Mastra instance](https://mastra.ai/reference/configuration) and a memory thread; otherwise the call falls through to a plain `resumeStream()`:

```typescript
const response = await agent.resumeStreamUntilIdle(
  { approved: true, selectedOption: 'plan-b' },
  {
    memory: {
      thread: 'thread-1',
      resource: 'resource-1',
    },
    runId: 'run-123',
    toolCallId: 'tool-call-456', // optional
    maxIdleMs: 5 * 60_000, //optional
  },
)

await response.processDataStream({
  onChunk: chunk => {
    console.log(chunk)
  },
})
```

The stream emits the same chunk types as `stream()`, plus `background-task-*` chunks for task lifecycle events. Visit [`Agent.streamUntilIdle()`](https://mastra.ai/reference/streaming/agents/streamUntilIdle) for the full server-side API and [background task chunks](https://mastra.ai/reference/streaming/ChunkType) for the payload shapes.

### `getTool()`

Retrieve information about a specific tool available to the agent:

```typescript
const tool = await agent.getTool('tool-id')
```

### `executeTool()`

Execute a specific tool for the agent:

```typescript
const result = await agent.executeTool('tool-id', {
  data: { input: 'value' },
})
```

### `network()`

Stream responses from an agent network for multi-agent interactions:

```typescript
const response = await agent.network('Research this topic and write a summary')

response.processDataStream({
  onChunk: async chunk => {
    console.log(chunk)
  },
})
```

### `approveToolCall()`

Approve a pending tool call and return a continuation stream. Use this when you are rendering the resumed chunks from the approval response.

```typescript
const response = await agent.approveToolCall({
  runId: 'run-123',
  toolCallId: 'tool-call-456',
})

response.processDataStream({
  onChunk: async chunk => {
    console.log(chunk)
  },
})
```

### `sendToolApproval()`

Approve or decline a pending tool call for a subscribed thread. Use this with `subscribeToThread()` when the resumed chunks should arrive through the existing thread subscription instead of a separate continuation stream.

```typescript
const result = await agent.sendToolApproval({
  resourceId: 'user-123',
  threadId: 'thread-456',
  toolCallId: 'tool-call-456',
  approved: true,
})

console.log(result.accepted)
```

Returns `{ accepted: true, runId: string, toolCallId?: string }`.

### `declineToolCall()`

Decline a pending tool call and return a continuation stream. Use this when you are rendering the resumed chunks from the decline response.

```typescript
const response = await agent.declineToolCall({
  runId: 'run-123',
  toolCallId: 'tool-call-456',
})

response.processDataStream({
  onChunk: async chunk => {
    console.log(chunk)
  },
})
```

### `resumeStream()`

Resume a suspended agent stream with custom data. Use this to continue execution after a suspension point, such as a workflow suspend within an agent:

```typescript
const response = await agent.resumeStream(
  { approved: true, selectedOption: 'plan-b' },
  {
    runId: 'run-123',
    toolCallId: 'tool-call-456', // optional
  },
)

await response.processDataStream({
  onChunk: chunk => {
    console.log(chunk)
  },
})
```

### `approveToolCallGenerate()`

Approve a pending tool call when using `generate()` (non-streaming). Returns the complete response:

```typescript
const output = await agent.generate('Find user John', {
  requireToolApproval: true,
})

if (output.finishReason === 'suspended') {
  const result = await agent.approveToolCallGenerate({
    runId: output.runId,
    toolCallId: output.suspendPayload.toolCallId,
  })

  console.log(result.text)
}
```

### `declineToolCallGenerate()`

Decline a pending tool call when using `generate()` (non-streaming). Returns the complete response:

```typescript
const output = await agent.generate('Find user John', {
  requireToolApproval: true,
})

if (output.finishReason === 'suspended') {
  const result = await agent.declineToolCallGenerate({
    runId: output.runId,
    toolCallId: output.suspendPayload.toolCallId,
  })

  console.log(result.text)
}
```

## Client tools

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

```typescript
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 inputData => {
    document.body.style.backgroundColor = inputData.color
    return { success: true }
  },
})

// Use with generate
const response = await agent.generate('Change the background to blue', {
  clientTools: { colorChangeTool },
})

// Use with stream
const response = await agent.stream('Tell me a story', {
  memory: {
    thread: 'thread-1',
    resource: 'resource-1',
  },
  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,
        )}`,
      )
    }
  },
})
```

### Tracing client tools

When `@mastra/observability` is installed and configured on the server, a client-side tool records a `CLIENT_TOOL_CALL` span as a child of the current `AGENT_RUN` span. The server creates that span when the model emits the client tool call, injects a W3C trace carrier into the outgoing tool-call chunk, and ends the span once the tool arguments are available. Without server-side observability configured, client tool tracing is a no-op.

The client SDK also measures the wall-clock duration of each client tool's `execute` function and ships it back to the server, where it's emitted as a `mastra_tool_duration_ms` metric with `toolType: "client"`.

For richer telemetry from inside your tool's `execute` function, use the `observe` helper on the execution context to add child spans and structured logs:

```typescript
import { createTool } from '@mastra/client-js'
import { z } from 'zod'

const fetchUserTool = createTool({
  id: 'fetchUser',
  description: 'Fetches the current user profile',
  inputSchema: z.object({ userId: z.string() }),
  execute: async ({ userId }, { observe }) => {
    observe.log('info', 'fetching user', { userId })
    const user = await observe.span('http GET /users', async () => {
      const res = await fetch(`/api/users/${userId}`)
      return res.json()
    })
    return user
  },
})
```

`observe` is always available — when no tracing context is active (e.g. running outside a traced agent), `span` runs the function directly and `log` is a no-op. No null-checking needed.

The SDK serializes everything the collector buffered as OTLP/JSON and ships it back in the next request body. The server's `@mastra/observability` package validates that the spans belong to the correct trace (preventing cross-trace injection) and forwards each span/log into the same observability bus that server-side telemetry uses. Your existing exporters pick them up automatically after observability is configured.

## Stored agents

Stored agents are agent configurations stored in a database that can be created, updated, and deleted at runtime. They reference primitives (tools, workflows, other agents, scorers) by key, which are resolved from the Mastra registry when the agent is instantiated. Memory is configured inline as a `SerializedMemoryConfig` object with options such as `lastMessages` and `semanticRecall`.

### `listStoredAgents()`

Retrieve a paginated list of all stored agents:

```typescript
const result = await mastraClient.listStoredAgents()
console.log(result.agents) // Array of stored agents
console.log(result.total) // Total count
```

With pagination and ordering:

```typescript
const result = await mastraClient.listStoredAgents({
  page: 0,
  perPage: 20,
  orderBy: {
    field: 'createdAt',
    direction: 'DESC',
  },
})
```

### `createStoredAgent()`

Create a new stored agent:

```typescript
const agent = await mastraClient.createStoredAgent({
  id: 'my-agent',
  name: 'My Assistant',
  instructions: 'You are a helpful assistant.',
  model: {
    provider: 'openai',
    name: 'gpt-5.4',
  },
})
```

With all options:

```typescript
const agent = await mastraClient.createStoredAgent({
  id: 'full-agent',
  name: 'Full Agent',
  description: 'A fully configured agent',
  instructions: 'You are a helpful assistant.',
  model: {
    provider: 'openai',
    name: 'gpt-5.4',
  },
  tools: { calculator: {}, weather: {} },
  workflows: { 'data-processing': {} },
  agents: { 'subagent-1': {} },
  memory: {
    options: {
      lastMessages: 20,
      semanticRecall: false,
    },
  },
  scorers: {
    'quality-scorer': {
      sampling: { type: 'ratio', rate: 0.1 },
    },
  },
  defaultOptions: {
    maxSteps: 10,
  },
  metadata: {
    version: '1.0',
    team: 'engineering',
  },
})
```

### `getStoredAgent()`

Get an instance of a specific stored agent:

```typescript
const storedAgent = mastraClient.getStoredAgent('my-agent')
```

## Stored agent methods

### `details()`

Retrieve the stored agent configuration:

```typescript
const details = await storedAgent.details()
console.log(details.name)
console.log(details.instructions)
console.log(details.model)
```

### `update()`

Update specific fields of a stored agent. All fields are optional:

```typescript
const updated = await storedAgent.update({
  name: 'Updated Agent Name',
  instructions: 'New instructions for the agent.',
})
```

```typescript
// Update just the tools
await storedAgent.update({
  tools: { 'new-tool-1': {}, 'new-tool-2': {} },
})

// Update metadata
await storedAgent.update({
  metadata: {
    version: '2.0',
    lastModifiedBy: 'admin',
  },
})
```

### `delete()`

Delete a stored agent:

```typescript
const result = await storedAgent.delete()
console.log(result.success) // true
```

## Version management

Both `Agent` (code-defined) and `StoredAgent` instances have methods for managing configuration versions. See the [Editor overview](https://mastra.ai/docs/editor/overview) for an introduction to version management.

### Getting an agent with a specific version

Pass a version identifier when getting an agent:

```typescript
// Load the published version (default)
const agent = mastraClient.getAgent('support-agent')

// Load the latest draft
const draftAgent = mastraClient.getAgent('support-agent', { status: 'draft' })

// Load a specific version
const versionedAgent = mastraClient.getAgent('support-agent', { versionId: 'abc-123' })
```

For stored agents, pass a status option to `details()`:

```typescript
const storedAgent = mastraClient.getStoredAgent('my-agent')
const draft = await storedAgent.details(undefined, { status: 'draft' })
```

### `listVersions()`

List all versions for an agent:

```typescript
const versions = await agent.listVersions()
console.log(versions.items) // Array of version snapshots
console.log(versions.total)
```

With pagination and sorting:

```typescript
const versions = await agent.listVersions({
  page: 0,
  perPage: 10,
  orderBy: {
    field: 'createdAt',
    direction: 'DESC',
  },
})
```

### `createVersion()`

Create a new version snapshot:

```typescript
const version = await agent.createVersion({
  changeMessage: 'Updated tone to be more friendly',
})
```

### `getVersion()`

Get a specific version by ID:

```typescript
const version = await agent.getVersion('version-123')
console.log(version.versionNumber)
console.log(version.changedFields)
console.log(version.createdAt)
```

### `activateVersion()`

Set a version as the active published version:

```typescript
await agent.activateVersion('version-123')
```

### `restoreVersion()`

Restore a previous version by creating a new version with the same configuration:

```typescript
await agent.restoreVersion('version-456')
```

### `deleteVersion()`

Delete a version:

```typescript
await agent.deleteVersion('version-789')
```

### `compareVersions()`

Compare two versions and return their differences:

```typescript
const diff = await agent.compareVersions('version-123', 'version-456')
console.log(diff.changes) // Fields that changed between versions
```

### React SDK

In the React SDK, pass an `agentVersionId` through `requestContext` when using the `useChat` hook:

```typescript
import { useChat } from '@mastra/react'

function Chat() {
  const { messages, input, handleInputChange, handleSubmit } = useChat({
    agentId: 'support-agent',
    requestContext: {
      agentVersionId: 'abc-123',
    },
  })

  // ... render chat UI
}
```