AXL cannot give you this information. You can only use AXL to send an SQL query to get from the extension (in the table nummplan) to the phone (in the table device).
Then, if you're on CCM 4.x, there's the DeviceListX.asp report which gives you the IP address. Refer to the IP Phone Services Developer Guide for more info.
Starting with CCM5 you need to use AXL Serviceability to get the information (first you send an SQL query via AXL to get from the extension to the phone, then get the phone's IP via AXL serviceability). Refer to the XML developer guide for more info on AXL serviceability.
Finally, the data dictionary will help you formulate the appropriate SQL query.
You can find all those douments here:
http://www.cisco.com/en/US/products/sw/voicesw/ps556/products_programming_reference_guides_list.html