tool-fallback

import {
ToolFallbackSample,
ToolFallbackRunningSample,
ToolFallbackCancelledSample,
ToolFallbackStreamingSample,
} from "@/components/docs/samples/tool-fallback";

Getting Started#

Add `tool-fallback`#

This adds a /components/assistant-ui/tool-fallback.tsx file to your project, which you can adjust as needed.

Use it in your application#

Pass the ToolFallback component to the MessagePrimitive.Parts component

import { ToolFallback } from "@/components/assistant-ui/tool-fallback";

const AssistantMessage = () => {
  return (
    <MessagePrimitive.Root>
      <MessagePrimitive.Parts>
        {({ part }) => {
          if (part.type === "tool-call") return <ToolFallback {...part} />;
          return null;
        }}
      </MessagePrimitive.Parts>
    </MessagePrimitive.Root>
  );
};

Examples#

Streaming Demo#

Interactive demo showing the full tool call lifecycle: running → complete.

Running State#

Shows a loading spinner and shimmer animation while the tool is executing.

Cancelled State#

Shows a muted appearance when a tool call was cancelled.

Composable API#

All sub-components are exported for custom layouts:

Component	Description
`ToolFallback.Root`	Collapsible container with scroll lock
`ToolFallback.Trigger`	Header with tool name, status icon, and shimmer
`ToolFallback.Content`	Animated collapsible content wrapper
`ToolFallback.Args`	Displays tool arguments
`ToolFallback.Result`	Displays tool execution result
`ToolFallback.Error`	Displays error or cancellation messages

import {
  ToolFallback,
  ToolFallbackRoot,
  ToolFallbackTrigger,
  ToolFallbackContent,
  ToolFallbackArgs,
  ToolFallbackResult,
  ToolFallbackError,
} from "@/components/assistant-ui/tool-fallback";

// Compound component syntax
<ToolFallback.Root>
  <ToolFallback.Trigger toolName="get_weather" status={status} />
  <ToolFallback.Content>
    <ToolFallback.Error status={status} />
    <ToolFallback.Args argsText={argsText} />
    <ToolFallback.Result result={result} />
  </ToolFallback.Content>
</ToolFallback.Root>

ToolGroup - Group consecutive tool calls together