> For the complete documentation index, see [llms.txt](https://docs.atfinity.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.atfinity.io/rule-language/operators/list-operators/contains.md). # contains ### Description `contains` is used to check a list of values, which is given on the left of the operator, against a single value on the right. ### Example A person can have multiple nationalities. If you want to include US tax documents if one of those nationalities is the United States, you could attach this condition to those [documents](/guides/glossary/document.md): ``` p is Person p.nationalities contains us ``` The list of nationalities of the person in this case should include `us` , meaning this condition evaluates to true and the documents to which it is attached will be included in the [case](/guides/glossary/case.md). --- # 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.atfinity.io/rule-language/operators/list-operators/contains.md?ask=&goal= ``` `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.