> For the complete documentation index, see [llms.txt](https://knowledgebase.fabricdata.com/xytech/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://knowledgebase.fabricdata.com/xytech/rest-api/custom-field-handling.md).

# Custom Field Handling

### Custom Fields

Any custom fields you have defined through document customization are automatically included in REST API definition. There is specific naming convention that is a combination of the Custom Code you created via document customisation plus the internal field name concatenated with an underscore. i.e. {customization code}\_{field name}

Document customization screen showing the user definable Customization Code 

<figure><img src="/files/dkXmxQk8z8GVrGlbd0By" alt=""><figcaption></figcaption></figure>

*Document customization screen showing the internal field names:*&#x20;

<figure><img src="/files/GL973gVP0hW2SNL6mtXp" alt=""><figcaption></figcaption></figure>

Response from a GET call to fetch a Work Order that shows custom fields:&#x20;

<figure><img src="/files/FAmfRo8fLBKYbUj1Yyg6" alt=""><figcaption></figcaption></figure>

### Custom drop-down fields with additional attributes

Users can enable **custom dropdown fields** (through enabling a document customisation flag 'Additional API details', so that when called by the REST API will return the additional attributes stored with the dropdown record such as external\_key.

Document Customisation fields showing additional checkbox:&#x20;

<figure><img src="/files/O7z13eHxq0OXrIgLIRxw" alt=""><figcaption></figcaption></figure>

Example of a custom drop-down field when 'Additional API details' is not enabled:&#x20;

<figure><img src="/files/ufZYSqYcOjawyOWpaJP4" alt=""><figcaption></figcaption></figure>

Example of a custom drop-down field when 'Additional API details' is enabled:&#x20;

<figure><img src="/files/OtXSG7n8beUSTTSkXIZV" alt=""><figcaption></figcaption></figure>


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:

```
GET https://knowledgebase.fabricdata.com/xytech/rest-api/custom-field-handling.md?ask=<question>&goal=<endgoal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.