> For the complete documentation index, see [llms.txt](https://docs.kognitos.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.kognitos.com/legacy/legacy-experience/books/custom-books/api-reference.md).

# API Reference

- [Concepts](https://docs.kognitos.com/legacy/legacy-experience/books/custom-books/api-reference/concepts.md): Understand concepts and how they are utilized in procedures.
- [Connections](https://docs.kognitos.com/legacy/legacy-experience/books/custom-books/api-reference/connections.md): Learn how to connect with third-party tools and services in your custom book project.
- [Docstrings](https://docs.kognitos.com/legacy/legacy-experience/books/custom-books/api-reference/docstrings.md): Understand how to format and write docstrings to ensure your Book is well-documented.
- [Decorators](https://docs.kognitos.com/legacy/legacy-experience/books/custom-books/api-reference/decorators.md)
- [@book](https://docs.kognitos.com/legacy/legacy-experience/books/custom-books/api-reference/decorators/book-decorator.md)
- [@concept](https://docs.kognitos.com/legacy/legacy-experience/books/custom-books/api-reference/decorators/concept-decorator.md)
- [@config](https://docs.kognitos.com/legacy/legacy-experience/books/custom-books/api-reference/decorators/config-decorator.md)
- [@connect](https://docs.kognitos.com/legacy/legacy-experience/books/custom-books/api-reference/decorators/connect-decorator.md)
- [@oauth](https://docs.kognitos.com/legacy/legacy-experience/books/custom-books/api-reference/decorators/oauth-decorator.md)
- [@oauthtoken](https://docs.kognitos.com/legacy/legacy-experience/books/custom-books/api-reference/decorators/oauthtoken-decorator.md)
- [@procedure](https://docs.kognitos.com/legacy/legacy-experience/books/custom-books/api-reference/decorators/procedure-decorator.md)
- [Enums](https://docs.kognitos.com/legacy/legacy-experience/books/custom-books/api-reference/enums.md)
- [FilterBinaryOperator](https://docs.kognitos.com/legacy/legacy-experience/books/custom-books/api-reference/enums/filterbinaryoperator-enum.md)
- [FilterUnaryOperator](https://docs.kognitos.com/legacy/legacy-experience/books/custom-books/api-reference/enums/filterunaryoperator-enum.md)
- [Filter Expressions](https://docs.kognitos.com/legacy/legacy-experience/books/custom-books/api-reference/enums/filter-expressions.md): Learn about implementing filter expressions in your custom book project.
- [Noun Phrases](https://docs.kognitos.com/legacy/legacy-experience/books/custom-books/api-reference/noun-phrases.md): Learn about the concept of a noun phrase.
- [Procedures](https://docs.kognitos.com/legacy/legacy-experience/books/custom-books/api-reference/procedures.md): Learn how to implement a procedure in a custom book.
- [Questions](https://docs.kognitos.com/legacy/legacy-experience/books/custom-books/api-reference/questions.md): Learn how to implement questions in a custom book.