> For the complete documentation index, see [llms.txt](https://docs.b2ihealthcare.com/snow-owl-authoring-platform/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.b2ihealthcare.com/snow-owl-authoring-platform/browsing-and-searching/searching/filter-search.md).

# Filter Search

The SNOMED CT hierarchy can be filtered by typing the search term in the entry field on the top of the view. The filtering is incremental, each keystroke is evaluated as you type. 

{% hint style="info" %}
All descriptions are considered during filtering, not only the preferred terms; you can also use the filter to look up a concept by its ID.
{% endhint %}

To reduce the number of keystrokes, you can enter only the first few characters of the words in a multi-word expression. For example, enter *`bl pr st sy`* to find `Standing systolic blood pressure`**.**

![Filter search for multi-word expression](/files/AW2Upv725fgXvmD0Gbzb)

The results can be presented either as a tree or as a flat list. Use the ![](/files/-M286fKCqX42-AeK1AlR) *Toggle between flat list and tree for filtered results* button to switch between the two options.

{% hint style="info" %}
These features are also available for other views including ICD-10, Local code systems,  and OPCS-4.
{% endhint %}


---

# 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://docs.b2ihealthcare.com/snow-owl-authoring-platform/browsing-and-searching/searching/filter-search.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.