Clarify description of `len()` function
@@ -251,8 +251,8 @@ Here are some examples of conditions you can use:
#### Functions
| Function | Description | Example |
-|:---------|:---------------------------------------------------------------------------------------------------------------|:-----------------------------------|
-| `len` | Returns the length of the object/slice. Works only with the `[BODY]` placeholder. | `len([BODY].username) > 8` |
+|:---------|:------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|:-----------------------------------|
+| `len` | If the given path leads to an array, returns its length. Otherwise, the JSON at the given path is minified and converted to a string, and the resulting number of characters is returned. Works only with the `[BODY]` placeholder. | `len([BODY].username) > 8` |
| `has` | Returns `true` or `false` based on whether a given path is valid. Works only with the `[BODY]` placeholder. | `has([BODY].errors) == false` |
| `pat` | Specifies that the string passed as parameter should be evaluated as a pattern. Works only with `==` and `!=`. | `[IP] == pat(192.168.*)` |
| `any` | Specifies that any one of the values passed as parameters is a valid value. Works only with `==` and `!=`. | `[BODY].ip == any(127.0.0.1, ::1)` |
