# Writing instructions manually

While Custom Parser helps you automate data parsing with AI-powered features, you can also write parsing instructions manually using CSS and XPath expressions. This gives you the option to **handle edge cases** or **customize parsing logic** for specific scenarios.

Custom Parser requires these mandatory parameters when creating a job:

* `parse` set to `true`
* `parsing_instructions` containing a JSON object with your extraction rules

Once you're happy with your custom parsing logic, you can save the instructions as a reusable [parser preset](/products/web-scraper-api/features/custom-parser/parser-presets.md).

Check out our comprehensive guides below, where you can find practical examples, best practices for XPath expressions, and a complete reference of all available parsing functions.

{% content-ref url="/pages/oxrwg37AyLWH1P5TPzwI" %}
[Parsing instruction examples](/products/web-scraper-api/features/custom-parser/writing-instructions-manually/parsing-instruction-examples.md)
{% endcontent-ref %}

{% content-ref url="/pages/z3HuH3Sn6WT2loO8bw5e" %}
[Tips for writing XPath expressions](/products/web-scraper-api/features/custom-parser/writing-instructions-manually/tips-for-writing-xpath-expressions.md)
{% endcontent-ref %}

{% content-ref url="/pages/751P6A1HZSfgMAhsniMo" %}
[List of parsing functions](/products/web-scraper-api/features/custom-parser/writing-instructions-manually/list-of-functions.md)
{% endcontent-ref %}

{% content-ref url="/pages/LWprqEz9Iwufi0fbGjXn" %}
[Parsing function examples](/products/web-scraper-api/features/custom-parser/writing-instructions-manually/list-of-functions/function-examples.md)
{% endcontent-ref %}


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# Agent Instructions: 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:

```
GET https://developers.oxylabs.io/products/web-scraper-api/features/custom-parser/writing-instructions-manually.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
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.