# What is a Function?

* Functions are displayed in the multiway select with their names, followed by parentheses (), indicating that they are a function. 

* If a function has parameters, these will be displayed alongside the expected parameter type within the parentheses, such as (string).

* When a function is selected in the multiway select, it will appear in a light blue color tag to indicate that it is currently selected. Any associated parameters for the selected function will be displayed on the next line.

* There are two types of Functions in Langstack applications: Static functions and Variable functions.
  * *Static functions* do not require a value to use them. 
    * Static Function is accessible directly from the Type by simply referencing the Type itself. Therefore, users must navigate to the Type first to reach its available functions. 
    * The available Static functions in Langstack applications are for the following Types: 
      * DateTime
      * GUID
      * Numerical
      * String
      * Timestamp

* *Variable functions* can only be accessed if a value exists. 
  * The value is either displayed as the function's returned result or is stored in a variable. 
  * To access the functions available for the value, users need to navigate further down (drill into) the value. 
  * When selecting a function, it is possible to call the functions available from the returned value to refine the desired result further. \
    For example: Type>Static Function>Returned Variable Function>Returned value of the returned value. 
  *  The value returned from the function can be stored in a variable. 
  * The Update Variable Action is used to update the variable with a value. 
  * The Value must be provided by the user or returned from a function.


---

# 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://docs.langstack.com/welcome/get-started/learn-langstack/basics-and-essentials/what-is-a-function.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.