> For the complete documentation index, see [llms.txt](https://docs.ont.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.ont.io/developer-tools/signing-server/api-reference.md).

# API reference

## API endpoint

The signing service is basically a `JSON` `RPC` server that is by default available at:

```
http://localhost:20000/cli
```

{% hint style="info" %}
The signing server only supports `POST`method queries
{% endhint %}

## Request structure

The request sent to the signing server is structured as follows:

```javascript
{
  qid: "XXX",      // Request ID. The response will echo back the same qid
  method: "XXX",   // Requested method name
  account: "XXX",  // Account for sign
  pwd: "XXX",      // Account password
  params: {}       // Input parameters for the requested method
}
```

## Response structure

The response sent by the signing server has the following structure:

```javascript
{
  qid: "XXX",         // Request ID
  method: "XXX",      // Requested method name
  result: {           // Response result
    signed_tx: "XXX"  // Signed transaction
  },
  error_code: 0,      // Error code，zero represents success, non-zero represents failure
  error_info: ""      // Error description
}
```

## Error codes

In case an error occurs, the `error_code` field will contain one of the following error codes:

| Error code | Error description         |
| :--------: | ------------------------- |
|    1001    | Invalid `http` method     |
|    1002    | Invalid `http` request    |
|    1003    | Invalid request parameter |
|    1004    | Unsupported method        |
|    1005    | Account is locked         |
|    1006    | Invalid transactions      |
|    1007    | `ABI` is not found        |
|    1008    | `ABI` is not matched      |
|    9999    | Unknown error             |

Please refer to the following links to find the relevant functions:

|       Library       | Link                                                                              |
| :-----------------: | --------------------------------------------------------------------------------- |
| Account information | <https://dev-docs.ont.io/#/docs-en/SignServer/04-api-account-methods>             |
|   Signing methods   | <https://dev-docs.ont.io/#/docs-en/SignServer/05-api-signing-methods>             |
| Convenience methods | <https://dev-docs.ont.io/#/docs-en/SignServer/06-api-signing-convinience-methods> |