Model Context

Configure assistant behavior through system instructions, tools, and context providers.

Model Context is the foundation of intelligence in assistant-ui components. It provides configuration and capabilities to the assistant through a context provider system.

Core Concepts

System Instructions

System instructions define the base behavior and knowledge available to the assistant. These can be provided in several ways:

import {
  useAssistantInstructions,
  useAssistantContext,
  makeAssistantVisible,
} from "@assistant-ui/react";

// Static instructions
useAssistantInstructions("You are a helpful assistant...");

// Dynamic context — callback is evaluated lazily at send-time
useAssistantContext({
  getContext: () => `Current page: ${window.location.href}`,
});

// Via makeAssistantVisible
const ReadableComponent = makeAssistantVisible(MyComponent);
// Automatically provides component HTML as system context

useAssistantInstructions takes a static string that re-registers when changed. useAssistantContext takes a callback that is evaluated fresh each time the model context is read, making it ideal for injecting frequently-changing application state without triggering re-registrations.

Tools

Tools are functions that the assistant can use to interact with your application. They can be provided through various mechanisms:

app/form-toolkit.tsx

"use generative";

import { defineToolkit } from "@assistant-ui/react";
import { z } from "zod";

export default defineToolkit({
  submitForm: {
    description: "Submit the form with the user's details.",
    parameters: z.object({
      email: z.string().email(),
      name: z.string(),
    }),
    execute: async ({ email, name }) => {
      "use client";
      // Implementation
      return { success: true };
    },
    renderText: { running: "Submitting…", complete: "Submitted" },
  },
});

app/Form.tsx

import {
  AuiProvider,
  makeAssistantVisible,
  Tools,
  useAui,
} from "@assistant-ui/react";
import toolkit from "./form-toolkit";

// Via makeAssistantVisible's clickable option
const ClickableButton = makeAssistantVisible(Button, {
  clickable: true, // Provides a click tool
});

// Use in your component
function Form() {
  const aui = useAui({ tools: Tools({ toolkit }) });

  return (
    <AuiProvider value={aui}>
      <form>{/* form fields */}</form>
    </AuiProvider>
  );
}

Context Provider System

The context provider system allows components to contribute to the model context. Here's a typical usage pattern:

import { useAui, tool } from "@assistant-ui/react";
import { useEffect } from "react";
import { z } from "zod";

// Define tool outside the component (no runtime dependencies)
const myTool = tool({
  parameters: z.object({
    query: z.string(),
  }),
  execute: async ({ query }) => {
    const result = await searchDatabase(query);
    return { result };
  },
});

function MyComponent() {
  const aui = useAui();

  useEffect(() => {
    // Register context provider
    return aui.modelContext().register({
      getModelContext: () => ({
        system: "You are a helpful search assistant...",
        tools: { myTool },
      }),
    });
  }, [aui]); // Re-register if api changes

  return <div>{/* component content */}</div>;
}

Provider Composition

Multiple providers can be registered, and their contexts will be composed:

System instructions are concatenated
Tool sets are merged
Nested readable components only contribute their context at the outermost level

Best Practices

System Instructions
- Keep them focused and specific to the component's purpose
- Use useAssistantInstructions for explicit instructions
- Let makeAssistantVisible handle component structure
Tools
- Use toolkit entries to define tool schemas and behavior
- Prefer Tools({ toolkit }) for reusable tools
- Handle errors gracefully
- Consider async operations and loading states
- Use the built-in click tool when possible
Context Management
- Register providers in useEffect for proper cleanup
- Clean up providers when components unmount
- Avoid deeply nested readable components
- Consider performance implications of large HTML structures