tools
Registers LLM tools and renders custom tool-call UI in assistant-ui (@assistant-ui/react). Use when adding frontend-only tools with makeAssistantTool / useAssistantTool (browser actions like clipboard, navigation, localStorage, async-generator streaming, AbortSignal), rendering backend AI SDK tool() calls with makeAssistantToolUI / useAssistantToolUI (status.type running/complete/incomplete/requires-action, args, result, artifact via ToolCallMessagePartProps), building generative UI from tool results, or implementing human-in-the-loop and approval flows (addResult, resume with context.human(), respondToApproval for server-side needsApproval gates). Covers registering tool components inside AssistantRuntimeProvider and the case-sensitive toolName matching that connects a tool to its UI. Reach for this when tool UI is not rendering, a tool is not being called, or a result is not showing.
What this skill does
# assistant-ui Tools
**Always consult [assistant-ui.com/llms.txt](https://www.assistant-ui.com/llms.txt) for the latest API.**
Tools let LLMs trigger actions with custom UI rendering.
## References
- [./references/make-tool.md](./references/make-tool.md) -- makeAssistantTool/useAssistantTool
- [./references/tool-ui.md](./references/tool-ui.md) -- makeAssistantToolUI rendering
- [./references/human-in-loop.md](./references/human-in-loop.md) -- Confirmation patterns
- [./references/toolkits.md](./references/toolkits.md) -- Toolkits and the Tools component
- [./references/mcp-server.md](./references/mcp-server.md) -- Server-side MCP tools
- [./references/generative-ui.md](./references/generative-ui.md) -- Declarative generative UI
- [./references/registry-components.md](./references/registry-components.md) -- ToolFallback, ToolGroup, Image renderers
## Tool Types
```
Where does the tool execute?
├─ Backend (LLM calls API) → AI SDK tool()
│ └─ Want custom UI? → makeAssistantToolUI
└─ Frontend (browser-only) → makeAssistantTool
└─ Want custom UI? → makeAssistantToolUI
```
## Backend Tool with UI
```ts
// Backend (app/api/chat/route.ts)
import { openai } from "@ai-sdk/openai";
import {
streamText,
tool,
stepCountIs,
convertToModelMessages,
type UIMessage,
} from "ai";
import { z } from "zod";
export async function POST(req: Request) {
const { messages }: { messages: UIMessage[] } = await req.json();
const result = streamText({
model: openai("gpt-4o"),
messages: await convertToModelMessages(messages),
stopWhen: stepCountIs(5),
tools: {
get_weather: tool({
description: "Get weather for a city",
inputSchema: z.object({ city: z.string() }),
execute: async ({ city }) => ({ temp: 22, city }),
}),
},
});
return result.toUIMessageStreamResponse();
}
```
```tsx
import { makeAssistantToolUI } from "@assistant-ui/react";
const WeatherToolUI = makeAssistantToolUI({
toolName: "get_weather",
render: ({ args, result, status }) => {
// status is an object; check status.type (not status === "running")
if (status.type === "running") return <div>Loading weather...</div>;
return <div>{result?.city}: {result?.temp}°C</div>;
},
});
<AssistantRuntimeProvider runtime={runtime}>
<WeatherToolUI />
<Thread />
</AssistantRuntimeProvider>
```
## Frontend-Only Tool
```tsx
import { makeAssistantTool } from "@assistant-ui/react";
import { z } from "zod";
const CopyTool = makeAssistantTool({
toolName: "copy_to_clipboard",
parameters: z.object({ text: z.string() }),
execute: async ({ text }) => {
await navigator.clipboard.writeText(text);
return { success: true };
},
});
<AssistantRuntimeProvider runtime={runtime}>
<CopyTool />
<Thread />
</AssistantRuntimeProvider>
```
## API Reference
```tsx
// makeAssistantToolUI render props (ToolCallMessagePartProps)
interface ToolCallMessagePartProps {
toolCallId: string;
toolName: string;
args: Record<string, unknown>;
argsText: string; // raw streamed JSON
result?: unknown;
isError?: boolean;
artifact?: unknown; // UI-only artifact attached to the result
// status is an OBJECT, not a string. Branch on status.type.
status:
| { type: "running" }
| { type: "complete" }
| { type: "incomplete"; reason: "cancelled" | "length" | "content-filter" | "other" | "error" }
| { type: "requires-action"; reason: "interrupt" };
// Supply a result from the renderer (instead of a tool execute function)
addResult: (result: unknown) => void;
// Resume a frontend tool paused via context.human(...)
resume: (payload: unknown) => void;
// Respond to a server-side approval gate
respondToApproval: (response: { approved: boolean; reason?: string }) => void;
}
```
## Human-in-the-Loop
```tsx
const DeleteToolUI = makeAssistantToolUI({
toolName: "delete_file",
render: ({ args, status, addResult }) => {
if (status.type === "requires-action") {
return (
<div>
<p>Delete {args.path}?</p>
<button onClick={() => addResult({ confirmed: true })}>Confirm</button>
<button onClick={() => addResult({ confirmed: false })}>Cancel</button>
</div>
);
}
return <div>File deleted</div>;
},
});
```
## Common Gotchas
**Tool UI not rendering**
- `toolName` must match exactly (case-sensitive)
- Register UI inside `AssistantRuntimeProvider`
**Tool not being called**
- Check tool description is clear
- Use `stopWhen: stepCountIs(n)` to allow multi-step
**Result not showing**
- Tool must return a value
- Check `status.type === "complete"` before accessing result
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