> ## Documentation Index
> Fetch the complete documentation index at: https://docs.base.org/llms.txt
> Use this file to discover all available pages before exploring further.

# Sign Messages

> Sign EIP-712 typed data and plain messages with your Base Account using Base MCP

## What it does

The `sign` tool requests a cryptographic signature from your Base Account. Like all write tools, it requires your approval in Base Account.

Two signature types are supported:

| Type                     | Standard | Use case                                          |
| ------------------------ | -------- | ------------------------------------------------- |
| `personal_sign` / `0x45` | EIP-191  | Simple text messages, SIWE auth challenges        |
| `typed_data` / `0x01`    | EIP-712  | Structured data, permit signatures, protocol auth |

## What you can ask

```text theme={null}
Sign this message: "I agree to the terms of service"
```

```text theme={null}
Sign in to this app using my Base Account
```

Signing is usually invoked by protocols or integrations, not directly prompted by users. Your assistant will handle the signing flow when a service requests it.

## How it works

<Steps>
  <Step title="Your assistant calls sign()">
    Passes the message type and payload to Base MCP.
  </Step>

  <Step title="You receive an approval link">
    Open the approval link to review what you're signing in Base Account — the message content is shown in full.
  </Step>

  <Step title="You approve">
    Confirm the signature in the approval UI.
  </Step>

  <Step title="Signature returned">
    Your assistant polls `get_request_status` to retrieve the completed signature, then passes it to the requesting service.
  </Step>
</Steps>

## Related guides

<CardGroup cols={2}>
  <Card title="Execute contract calls" icon="code" href="/agents/guides/batch-calls">
    Batch multiple contract interactions into one approval.
  </Card>

  <Card title="Native plugins" icon="puzzle-piece" href="/agents/plugins/native">
    Moonwell, Uniswap, Avantis, and other protocol plugins — approval and signing patterns in the skill repo.
  </Card>
</CardGroup>