📄 ai-sdk/docs/troubleshooting/tool-invocation-missing-result

When using generateText() or streamText(), you may encounter the error "ToolInvocation must have a result" when a tool without an execute function is called.

Cause

The error occurs when you define a tool without an execute function and don't provide the result through other means (like useChat's onToolCall or addToolOutput functions).

Each time a tool is invoked, the model expects to receive a result before continuing the conversation. Without a result, the model cannot determine if the tool call succeeded or failed and the conversation state becomes invalid.

Solution

You have two options for handling tool results:

Server-side execution using tools with an execute function:

const tools = { weather: tool({ description: 'Get the weather in a location', parameters: z.object({ location: z .string() .describe('The city and state, e.g. "San Francisco, CA"'), }), execute: async ({ location }) => { // Fetch and return weather data return { temperature: 72, conditions: 'sunny', location }; }, }),};
Client-side execution with useChat (omitting the execute function), you must provide results using addToolOutput:

import { useChat } from '@ai-sdk/react';import { DefaultChatTransport, lastAssistantMessageIsCompleteWithToolCalls,} from 'ai'; const { messages, sendMessage, addToolOutput } = useChat({ // Automatically submit when all tool results are available sendAutomaticallyWhen: lastAssistantMessageIsCompleteWithToolCalls, // Handle tool calls in onToolCall onToolCall: async ({ toolCall }) => { if (toolCall.toolName === 'getLocation') { try { const result = await getLocationData(); // Important: Don't await inside onToolCall to avoid deadlocks addToolOutput({ tool: 'getLocation', toolCallId: toolCall.toolCallId, output: result, }); } catch (err) { // Important: Don't await inside onToolCall to avoid deadlocks addToolOutput({ tool: 'getLocation', toolCallId: toolCall.toolCallId, state: 'output-error', errorText: 'Failed to get location', }); } } },});

// For interactive UI elements:const { messages, sendMessage, addToolOutput } = useChat({ transport: new DefaultChatTransport({ api: '/api/chat' }), sendAutomaticallyWhen: lastAssistantMessageIsCompleteWithToolCalls,}); // Inside your JSX, when rendering tool calls:<button onClick={() => addToolOutput({ tool: 'myTool', toolCallId, // must provide tool call ID output: { /* your tool result */ }, }) }> Confirm</button>;

Whether handling tools on the server or client, each tool call must have a corresponding result before the conversation can continue.

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Tool Invocation Missing Result Error

Issue

Cause

Solution

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