# ChatMCPOptions

# Interface: ChatMCPOptions

Defined in: [packages/ai/src/activities/chat/mcp/types.ts:32](https://github.com/TanStack/ai/blob/main/packages/ai/src/activities/chat/mcp/types.ts#L32)

Options controlling MCP tool discovery and lifecycle for a `chat()` call.

## Properties

### clients

```ts
clients: MCPToolSource[];
```

Defined in: [packages/ai/src/activities/chat/mcp/types.ts:36](https://github.com/TanStack/ai/blob/main/packages/ai/src/activities/chat/mcp/types.ts#L36)

The MCP clients or client pools to discover tools from and manage.

***

### connection?

```ts
optional connection: MCPConnectionPolicy;
```

Defined in: [packages/ai/src/activities/chat/mcp/types.ts:43](https://github.com/TanStack/ai/blob/main/packages/ai/src/activities/chat/mcp/types.ts#L43)

Connection lifecycle policy applied to all clients when the run ends.

Defaults to `'close'`.

***

### lazyTools?

```ts
optional lazyTools: boolean;
```

Defined in: [packages/ai/src/activities/chat/mcp/types.ts:51](https://github.com/TanStack/ai/blob/main/packages/ai/src/activities/chat/mcp/types.ts#L51)

When `true`, tool schemas are fetched lazily (forwarded to
`tools({ lazy: true })`).

Defaults to `false`.

***

### onDiscoveryError()?

```ts
optional onDiscoveryError: (error, source) => void | Promise<void>;
```

Defined in: [packages/ai/src/activities/chat/mcp/types.ts:62](https://github.com/TanStack/ai/blob/main/packages/ai/src/activities/chat/mcp/types.ts#L62)

Called when tool discovery fails for a single source.

- Throw (or re-throw) from this handler to fail the entire chat call fast.
- Return normally to skip that source and continue with remaining clients.
- Omit this handler entirely to rethrow the error (fail-fast by default).

Async handlers are awaited, so a rejected promise also fails fast.

#### Parameters

##### error

`unknown`

##### source

[`MCPToolSource`](MCPToolSource.md)

#### Returns

`void` \| `Promise`\<`void`\>