Chatbot Tool Usage | AI SDK 简体中文

With useChat and streamText, you can use tools in your chatbot application. The AI SDK supports three tool execution patterns in this context:

Automatically executed server-side tools
Automatically executed client-side tools
Tools that require user interaction, such as confirmation dialogs

The flow is as follows:

The user enters a message in the chat UI.
The message is sent to the API route.
In your server-side route, the language model generates tool calls during the streamText call.
All tool calls are forwarded to the client.
Server-side tools are executed using their execute method and their results are forwarded to the client.
Client-side tools that should be automatically executed are handled with the onToolCall callback. You must call addToolOutput to provide the tool result.
Client-side tools that require user interactions can be displayed in the UI. The tool calls and results are available as tool invocation parts in the parts property of the last assistant message.
When the user interaction is done, addToolOutput can be used to add the tool result to the chat.
The chat can be configured to automatically submit when all tool results are available using sendAutomaticallyWhen. This triggers another iteration of this flow.

The tool calls and tool executions are integrated into the assistant message as typed tool parts. A tool part is at first a tool call, and then it becomes a tool result when the tool is executed. The tool result contains all information about the tool call as well as the result of the tool execution.

Note

Tool result submission can be configured using the sendAutomaticallyWhen option. You can use the lastAssistantMessageIsCompleteWithToolCalls helper to automatically submit when all tool results are available. This simplifies the client-side code while still allowing full control when needed.

Example

In this example, we'll use three tools:

getWeatherInformation: An automatically executed server-side tool that returns the weather in a given city.
askForConfirmation: A user-interaction client-side tool that asks the user for confirmation.
getLocation: An automatically executed client-side tool that returns a random city.

API route

import {
  convertToModelMessages,
  createUIMessageStreamResponse,
  streamText,
  toUIMessageStream,
  UIMessage,
} from 'ai';
import { z } from 'zod';

// Allow streaming responses up to 30 seconds
export const maxDuration = 30;

export async function POST(req: Request) {
  const { messages }: { messages: UIMessage[] } = await req.json();

  const result = streamText({
    model: 'anthropic/claude-sonnet-5.5',
    messages: await convertToModelMessages(messages),
    tools: {
      // server-side tool with execute function:
      getWeatherInformation: {
        description: 'show the weather in a given city to the user',
        inputSchema: z.object({ city: z.string() }),
        execute: async ({}: { city: string }) => {
          const weatherOptions = ['sunny', 'cloudy', 'rainy', 'snowy', 'windy'];
          return weatherOptions[
            Math.floor(Math.random() * weatherOptions.length)
          ];
        },
      },
      // client-side tool that starts user interaction:
      askForConfirmation: {
        description: 'Ask the user for confirmation.',
        inputSchema: z.object({
          message: z.string().describe('The message to ask for confirmation.'),
        }),
      },
      // client-side tool that is automatically executed on the client:
      getLocation: {
        description:
          'Get the user location. Always ask for confirmation before using this tool.',
        inputSchema: z.object({}),
      },
    },
  });

  return createUIMessageStreamResponse({
    stream: toUIMessageStream({ stream: result.stream }),
  });
}

Client-side page

The client-side page uses the useChat hook to create a chatbot application with real-time message streaming. Tool calls are displayed in the chat UI as typed tool parts. Please make sure to render the messages using the parts property of the message.

There are three things worth mentioning:

The onToolCall callback is used to handle client-side tools that should be automatically executed. In this example, the getLocation tool is a client-side tool that returns a random city. You call addToolOutput to provide the result (without await to avoid potential deadlocks).

Note
Always check if (toolCall.dynamic) first in your onToolCall handler. Without this check, TypeScript will throw an error like: Type 'string' is not assignable to type '"toolName1" | "toolName2"' when you try to use toolCall.toolName in addToolOutput.
The sendAutomaticallyWhen option with lastAssistantMessageIsCompleteWithToolCalls helper automatically submits when all tool results are available.
The parts array of assistant messages contains tool parts with typed names like tool-askForConfirmation. The client-side tool askForConfirmation is displayed in the UI. It asks the user for confirmation and displays the result once the user confirms or denies the execution. The result is added to the chat using addToolOutput with the tool parameter for type safety.

Typed tool parts also include the approval-requested, approval-responded, and output-denied states. Include these states when handling part.state exhaustively, even when a tool does not require approval. See Tool execution approval for a complete approval UI.

'use client';

import { useChat } from '@ai-sdk/react';
import {
  DefaultChatTransport,
  lastAssistantMessageIsCompleteWithToolCalls,
} from 'ai';
import { useState } from 'react';

export default function Chat() {
  const { messages, sendMessage, addToolOutput } = useChat({
    transport: new DefaultChatTransport({
      api: '/api/chat',
    }),

    sendAutomaticallyWhen: lastAssistantMessageIsCompleteWithToolCalls,

    // run client-side tools that are automatically executed:
    async onToolCall({ toolCall }) {
      // Check if it's a dynamic tool first for proper type narrowing
      if (toolCall.dynamic) {
        return;
      }

      if (toolCall.toolName === 'getLocation') {
        const cities = ['New York', 'Los Angeles', 'Chicago', 'San Francisco'];

        // No await - avoids potential deadlocks
        addToolOutput({
          tool: 'getLocation',
          toolCallId: toolCall.toolCallId,
          output: cities[Math.floor(Math.random() * cities.length)],
        });
      }
    },
  });
  const [input, setInput] = useState('');

  return (
    <>
      {messages?.map(message => (
        <div key={message.id}>
          <strong>{`${message.role}: `}</strong>
          {message.parts.map(part => {
            switch (part.type) {
              // render text parts as simple text:
              case 'text':
                return part.text;

              // for tool parts, use the typed tool part names:
              case 'tool-askForConfirmation': {
                const callId = part.toolCallId;

                switch (part.state) {
                  case 'input-streaming':
                    return (
                      <div key={callId}>Loading confirmation request...</div>
                    );
                  case 'input-available':
                    return (
                      <div key={callId}>
                        {part.input.message}
                        <div>
                          <button
                            onClick={() =>
                              addToolOutput({
                                tool: 'askForConfirmation',
                                toolCallId: callId,
                                output: 'Yes, confirmed.',
                              })
                            }
                          >
                            Yes
                          </button>
                          <button
                            onClick={() =>
                              addToolOutput({
                                tool: 'askForConfirmation',
                                toolCallId: callId,
                                output: 'No, denied',
                              })
                            }
                          >
                            No
                          </button>
                        </div>
                      </div>
                    );
                  case 'approval-requested':
                    return <div key={callId}>Approval requested.</div>;
                  case 'approval-responded':
                    return <div key={callId}>Approval response received.</div>;
                  case 'output-available':
                    return (
                      <div key={callId}>Confirmation result: {part.output}</div>
                    );
                  case 'output-error':
                    return <div key={callId}>Error: {part.errorText}</div>;
                  case 'output-denied':
                    return <div key={callId}>Tool call denied.</div>;
                }
                break;
              }

              case 'tool-getLocation': {
                const callId = part.toolCallId;

                switch (part.state) {
                  case 'input-streaming':
                    return (
                      <div key={callId}>Preparing location request...</div>
                    );
                  case 'input-available':
                    return <div key={callId}>Getting location...</div>;
                  case 'approval-requested':
                    return <div key={callId}>Approval requested.</div>;
                  case 'approval-responded':
                    return <div key={callId}>Approval response received.</div>;
                  case 'output-available':
                    return <div key={callId}>Location: {part.output}</div>;
                  case 'output-error':
                    return (
                      <div key={callId}>
                        Error getting location: {part.errorText}
                      </div>
                    );
                  case 'output-denied':
                    return <div key={callId}>Location request denied.</div>;
                }
                break;
              }

              case 'tool-getWeatherInformation': {
                const callId = part.toolCallId;

                switch (part.state) {
                  // example of pre-rendering streaming tool inputs:
                  case 'input-streaming':
                    return (
                      <pre key={callId}>{JSON.stringify(part, null, 2)}</pre>
                    );
                  case 'input-available':
                    return (
                      <div key={callId}>
                        Getting weather information for {part.input.city}...
                      </div>
                    );
                  case 'approval-requested':
                    return <div key={callId}>Approval requested.</div>;
                  case 'approval-responded':
                    return <div key={callId}>Approval response received.</div>;
                  case 'output-available':
                    return (
                      <div key={callId}>
                        Weather in {part.input.city}: {part.output}
                      </div>
                    );
                  case 'output-error':
                    return (
                      <div key={callId}>
                        Error getting weather for {part.input.city}:{' '}
                        {part.errorText}
                      </div>
                    );
                  case 'output-denied':
                    return <div key={callId}>Weather request denied.</div>;
                }
                break;
              }
            }
          })}
          <br />
        </div>
      ))}

      <form
        onSubmit={e => {
          e.preventDefault();
          if (input.trim()) {
            sendMessage({ text: input });
            setInput('');
          }
        }}
      >
        <input value={input} onChange={e => setInput(e.target.value)} />
      </form>
    </>
  );
}

Error handling

Sometimes an error may occur during client-side tool execution. Use the addToolOutput method with a state of output-error and errorText value instead of output to record the error.

'use client';

import { useChat } from '@ai-sdk/react';
import {
  DefaultChatTransport,
  lastAssistantMessageIsCompleteWithToolCalls,
} from 'ai';
import { useState } from 'react';

export default function Chat() {
  const { messages, sendMessage, addToolOutput } = useChat({
    transport: new DefaultChatTransport({
      api: '/api/chat',
    }),

    sendAutomaticallyWhen: lastAssistantMessageIsCompleteWithToolCalls,

    // run client-side tools that are automatically executed:
    async onToolCall({ toolCall }) {
      // Check if it's a dynamic tool first for proper type narrowing
      if (toolCall.dynamic) {
        return;
      }

      if (toolCall.toolName === 'getLocation') {
        try {
          const location = await getLocation();

          // No await - avoids potential deadlocks
          addToolOutput({
            tool: 'getLocation',
            toolCallId: toolCall.toolCallId,
            output: location,
          });
        } catch (err) {
          addToolOutput({
            tool: 'getLocation',
            toolCallId: toolCall.toolCallId,
            state: 'output-error',
            errorText: 'Unable to get the user location',
          });
        }
      }
    },
  });
}

When rendering messages, use isToolOutputErrorUIPart to identify failed static and dynamic tool parts without checking the tool state directly:

import { isToolOutputErrorUIPart, type UIMessage } from 'ai';

function ToolError({ part }: { part: UIMessage['parts'][number] }) {
  if (!isToolOutputErrorUIPart(part)) {
    return null;
  }

  return <div role="alert">{part.errorText}</div>;
}

Tool Execution Approval

Tool execution approval lets you require user confirmation before a server-side tool runs. Unlike client-side tools that execute in the browser, tools with approval still execute on the server—but only after the user approves.

Use tool execution approval when you want to:

Confirm sensitive operations (payments, deletions, external API calls)
Let users review tool inputs before execution
Add human oversight to automated workflows

For tools that need to run in the browser (updating UI state, accessing browser APIs), use client-side tools instead.

Server Setup

Enable approval with toolApproval on streamText. The older needsApproval property on tools is deprecated. See Tool Execution Approval for configuration options including dynamic approval based on input.

import {
  createUIMessageStreamResponse,
  streamText,
  tool,
  toUIMessageStream,
} from 'ai';
import { z } from 'zod';

export async function POST(req: Request) {
  const { messages } = await req.json();

  const result = streamText({
    model: 'anthropic/claude-sonnet-5.5',
    messages,
    tools: {
      getWeather: tool({
        description: 'Get the weather in a location',
        inputSchema: z.object({
          city: z.string(),
        }),
        execute: async ({ city }) => {
          const weather = await fetchWeather(city);
          return weather;
        },
      }),
    },
    toolApproval: {
      getWeather: 'user-approval',
    },
  });

  return createUIMessageStreamResponse({
    stream: toUIMessageStream({ stream: result.stream }),
  });
}

Client-Side Approval UI

When a tool requires manual approval, the tool part state is approval-requested. Automatic approvals and denials also flow through the same approval states, but they set part.approval.isAutomatic === true, so you can render the status without calling addToolApprovalResponse. Automatic approval decisions can also include part.approval.reason.

'use client';

import { useChat } from '@ai-sdk/react';

export default function Chat() {
  const { messages, addToolApprovalResponse } = useChat();

  return (
    <>
      {messages.map(message => (
        <div key={message.id}>
          {message.parts.map(part => {
            if (part.type === 'tool-getWeather') {
              switch (part.state) {
                case 'approval-requested': {
                  if (part.approval.isAutomatic) {
                    return (
                      <div key={part.toolCallId}>
                        Checking approval for {part.input.city}...
                      </div>
                    );
                  }

                  return (
                    <div key={part.toolCallId}>
                      <p>Get weather for {part.input.city}?</p>
                      {part.approval.requestReason && (
                        <p>{part.approval.requestReason}</p>
                      )}
                      <button
                        onClick={() =>
                          addToolApprovalResponse({
                            id: part.approval.id,
                            approved: true,
                          })
                        }
                      >
                        Approve
                      </button>
                      <button
                        onClick={() =>
                          addToolApprovalResponse({
                            id: part.approval.id,
                            approved: false,
                          })
                        }
                      >
                        Deny
                      </button>
                    </div>
                  );
                }
                case 'approval-responded':
                  return (
                    <div key={part.toolCallId}>
                      Weather request for {part.input.city} was
                      {part.approval.isAutomatic ? ' automatically' : ''}{' '}
                      {part.approval.approved ? 'approved' : 'denied'}.
                      {part.approval.reason
                        ? ` Reason: ${part.approval.reason}`
                        : ''}
                    </div>
                  );
                case 'output-available':
                  return (
                    <div key={part.toolCallId}>
                      Weather in {part.input.city}: {part.output}
                    </div>
                  );
                case 'output-denied':
                  return (
                    <div key={part.toolCallId}>
                      Weather request for {part.input.city} was denied.
                      {part.approval.reason
                        ? ` Reason: ${part.approval.reason}`
                        : ''}
                    </div>
                  );
              }
            }
            // Handle other part types...
          })}
        </div>
      ))}
    </>
  );
}

Call addToolApprovalResponse only for manual approvals. Automatic approval decisions already arrive in the UI stream as approval-requested and approval-responded states, and denied executions continue to output-denied. If you return a reason from an automatic approval or denial, it is available as part.approval.reason. For manual approval requests, the reason for requiring approval is available as part.approval.requestReason. It remains separate from an optional response reason supplied to addToolApprovalResponse. When a response reason is supplied with a denial, it is included in the execution-denied tool result that the model sees. When it is supplied with an approval for a tool executed by the AI SDK, it is recorded on the message part, but the SDK does not include it in the model prompt, modify the tool's input, or expose it through a dedicated execution option. To collect input from the user for a tool, use a client-side tool and addToolOutput instead.

Approval request chunks can also include an approvalDescriptor with opaque application-specific metadata. UI message processing exposes it as part.approval.descriptor in the approval-requested state and preserves it in subsequent approval-bearing states, including approval-responded. This lets clients render or persist server-computed approval metadata without using it to determine whether the tool was approved.

Securing Approvals for Sensitive Tools

In the useChat pattern, the client sends the full message history to the server each turn. Without additional protection, a modified client could fabricate an approval response. For tools that perform sensitive operations, add experimental_toolApprovalSecret to your streamText call so the server cryptographically verifies that it issued the approval:

const result = streamText({
  model: 'anthropic/claude-sonnet-5.5',
  messages,
  tools: { deleteFile },
  toolApproval: { deleteFile: 'user-approval' },
  experimental_toolApprovalSecret: process.env.TOOL_APPROVAL_SECRET,
});

See Security Considerations for setup details.

Auto-Submit After Approval

Note

If nothing happens after you approve a tool execution, make sure you either call sendMessage manually or configure sendAutomaticallyWhen on the useChat hook.

Use lastAssistantMessageIsCompleteWithApprovalResponses to automatically continue the conversation after approvals:

import { useChat } from '@ai-sdk/react';
import { lastAssistantMessageIsCompleteWithApprovalResponses } from 'ai';

const { messages, addToolApprovalResponse } = useChat({
  sendAutomaticallyWhen: lastAssistantMessageIsCompleteWithApprovalResponses,
});

Dynamic Tools

When using dynamic tools (tools with unknown types at compile time), the UI parts use a generic dynamic-tool type instead of specific tool types:

{
  message.parts.map((part, index) => {
    switch (part.type) {
      // Static tools with specific (`tool-${toolName}`) types
      case 'tool-getWeatherInformation':
        return <WeatherDisplay part={part} />;

      // Dynamic tools use generic `dynamic-tool` type
      case 'dynamic-tool':
        return (
          <div key={index}>
            <h4>Tool: {part.toolName}</h4>
            {part.state === 'input-streaming' && (
              <pre>{JSON.stringify(part.input, null, 2)}</pre>
            )}
            {part.state === 'output-available' && (
              <pre>{JSON.stringify(part.output, null, 2)}</pre>
            )}
            {part.state === 'output-error' && (
              <div>Error: {part.errorText}</div>
            )}
          </div>
        );
    }
  });
}

Dynamic tools are useful when integrating with:

MCP (Model Context Protocol) tools without schemas
User-defined functions loaded at runtime
External tool providers

Tool call streaming

Tool call streaming is enabled by default in AI SDK 5.0, allowing you to stream tool calls while they are being generated. This provides a better user experience by showing tool inputs as they are generated in real-time.

export async function POST(req: Request) {
  const { messages }: { messages: UIMessage[] } = await req.json();

  const result = streamText({
    model: 'anthropic/claude-sonnet-5.5',
    messages: await convertToModelMessages(messages),
    // toolCallStreaming is enabled by default in v5
    // ...
  });

  return createUIMessageStreamResponse({
    stream: toUIMessageStream({ stream: result.stream }),
  });
}

With tool call streaming enabled, partial tool calls are streamed as part of the data stream. They are available through the useChat hook. The typed tool parts of assistant messages will also contain partial tool calls. You can use the state property of the tool part to render the correct UI.

export default function Chat() {
  // ...
  return (
    <>
      {messages?.map(message => (
        <div key={message.id}>
          {message.parts.map(part => {
            switch (part.type) {
              case 'tool-askForConfirmation':
              case 'tool-getLocation':
              case 'tool-getWeatherInformation':
                switch (part.state) {
                  case 'input-streaming':
                    return <pre>{JSON.stringify(part.input, null, 2)}</pre>;
                  case 'input-available':
                    return <pre>{JSON.stringify(part.input, null, 2)}</pre>;
                  case 'approval-requested':
                    return <div>Approval requested.</div>;
                  case 'approval-responded':
                    return <div>Approval response received.</div>;
                  case 'output-available':
                    return <pre>{JSON.stringify(part.output, null, 2)}</pre>;
                  case 'output-error':
                    return <div>Error: {part.errorText}</div>;
                  case 'output-denied':
                    return <div>Tool call denied.</div>;
                }
            }
          })}
        </div>
      ))}
    </>
  );
}

Step start parts

When you are using multi-step tool calls, the AI SDK will add step start parts to the assistant messages. If you want to display boundaries between tool calls, you can use the step-start parts as follows:

// ...
// where you render the message parts:
message.parts.map((part, index) => {
  switch (part.type) {
    case 'step-start':
      // show step boundaries as horizontal lines:
      return index > 0 ? (
        <div key={index} className="text-gray-500">
          <hr className="my-2 border-gray-300" />
        </div>
      ) : null;
    case 'text':
    // ...
    case 'tool-askForConfirmation':
    case 'tool-getLocation':
    case 'tool-getWeatherInformation':
    // ...
  }
});
// ...

Server-side Multi-Step Calls

You can also use multi-step calls on the server-side with streamText. This works when all invoked tools have an execute function on the server side.

import {
  convertToModelMessages,
  createUIMessageStreamResponse,
  isStepCount,
  streamText,
  toUIMessageStream,
  UIMessage,
} from 'ai';
import { z } from 'zod';

export async function POST(req: Request) {
  const { messages }: { messages: UIMessage[] } = await req.json();

  const result = streamText({
    model: 'anthropic/claude-sonnet-5.5',
    messages: await convertToModelMessages(messages),
    tools: {
      getWeatherInformation: {
        description: 'show the weather in a given city to the user',
        inputSchema: z.object({ city: z.string() }),
        // tool has execute function:
        execute: async ({}: { city: string }) => {
          const weatherOptions = ['sunny', 'cloudy', 'rainy', 'snowy', 'windy'];
          return weatherOptions[
            Math.floor(Math.random() * weatherOptions.length)
          ];
        },
      },
    },
    stopWhen: isStepCount(5),
  });

  return createUIMessageStreamResponse({
    stream: toUIMessageStream({ stream: result.stream }),
  });
}

Errors

Language models can make errors when calling tools. By default, these errors are masked for security reasons, and show up as "An error occurred" in the UI.

Tool execution errors marked providerExecuted: true bypass this masking and the UI stream's onError callback. String errors pass through unchanged; other error values are serialized with JSON.stringify. The original error data is needed when converting persisted UI messages back into model messages, for example to preserve Anthropic tool error codes. Harness runtime tool errors also retain their original messages. The callback still handles invalid tool calls and stream errors, regardless of whether a tool is provider-executed.

To customize masked errors, pass onError to toUIMessageStream. This callback does not redact provider-executed tool execution errors sent to the client.

export function errorHandler(error: unknown) {
  if (error == null) {
    return 'unknown error';
  }

  if (typeof error === 'string') {
    return error;
  }

  if (error instanceof Error) {
    return error.message;
  }

  return JSON.stringify(error);
}

const result = streamText({
  // ...
});

return createUIMessageStreamResponse({
  stream: toUIMessageStream({
    stream: result.stream,
    onError: errorHandler,
  }),
});

In case you are using createUIMessageResponse, you can use the onError function when calling toUIMessageResponse:

const response = createUIMessageResponse({
  // ...
  async execute(dataStream) {
    // ...
  },
  onError: error => `Custom error: ${error.message}`,
});