I have a suggestion for the API documentation. In most API calls I miss an explanation about what the return value of a function actually is. For example
http://www.modxcms.com/dbapi-update.html From the information about the function I don't know what the value of $rows_affected is supposed to be after I call the API function. Does it return the number of rows that were updated? Does it return true if the update was succesfull and false if the update failed? The only way to figure it out is by reading the code

The nice thing about an API is that you don't have to know about how the function is implemented, only how you need to call it.
Also the code that is shown in the documentation does not match the code in MODx itself. I would suggest to remove the code from the documentation. It is just too hard to keep it in sync with each release and is not needed cause if someone wants to have a look at the code you can just look into the MODx code.