---
title: "Models & tools"
description: "Choose a Vercel AI SDK v6 model and build request-scoped tools with guaranteed cleanup."
---

A model is required in code unless hosted configuration supplies one. A store is
also required by the current handler.

## Model selection

```ts
createChatHandler({
  getUserId: getChatUserId,
  model: anthropic('claude-sonnet-4-5'),
  store: createDrizzleChatStore(),
});
```

For per-user selection, pass a function of the verified request context:

```ts
createChatHandler({
  getUserId: getChatUserId,
  store: createDrizzleChatStore(),
  model: async (ctx) => {
    const plan = await getUserPlan(ctx.userId);
    return plan === 'pro'
      ? anthropic('claude-sonnet-4-5')
      : openai('gpt-4o');
  },
});
```

`@mordn/chat-widget/models` exports `MODELS`, the package's hosted gateway-string
catalog. Provider SDK calls use provider-native ids; hosted config uses gateway
strings such as `anthropic/claude-sonnet-4-5`.

## Request-scoped tools

```ts
import { tool } from 'ai';
import { z } from 'zod';

createChatHandler({
  getUserId: getChatUserId,
  model,
  store,
  buildTools: async (ctx) => {
    const client = await connectMcp(ctx.userId);

    return {
      tools: {
        searchDocs: tool({
          description: 'Search the documentation.',
          inputSchema: z.object({ query: z.string() }),
          execute: async ({ query }) => client.search(query),
        }),
      },
      cleanup: () => client.close(),
    };
  },
});
```

AI SDK v6 tool definitions use `inputSchema`. Do not copy v5 examples that use
`parameters`.

`cleanup` runs exactly once after success, error, or abort. Use it for MCP
clients, transactions, or other per-request resources. Omit it for stateless
tools.

## Client tool rendering

`toolRenderers` receives `ToolPartLike` and may render custom JSX. Return `null`
to fall through to the default row. Use `actionRenderers` when a declarative
status card is enough, and derive status from actual tool state/output.

See [MCP tools](/docs/guides/mcp) and [AI UX extras](/docs/guides/ai-ux).