Author's note: for the overview post on ancient Maya gods and goddesses, go here.
God P is a god who so far has only been found in the Madrid Codex. He is much debated upon, with various theories connected to his function -- and in fact his existence as a god.
God P's notable feature is his fingers, which look frog-like, and he wears a headdress that incorporates a 360-day sign. Schellhas called it the Frog God, which is another name still used for the god.
In the Madrid Codex he is drawn making furrows and planting seeds, and this has been used as evidence of of the god being related to agriculture. However, there is a variance in how this is specifically interpreted. Two of my three sources with information on God P state that he is a god of agriculture. However, my third source South and Meso-American Mythology A to Z, states that God P is a water god related to agriculture.
Consideration: Only An Aspect?
God P may not be a god in his own right. He may just be an aspect of Pauahtun (God N) -- a god with at least four aspects ( known as Bacabs or Bakabs) who were thought to hold the sky.
There is a theory which states that God P is somehow Kukulkan/Quetzalcoatl (the Aztec version of Kukulkan), and several theorists on this are Tedlock, Seler and Taube. In particular Taube thinks that God P is a form of Kukulkan/Queztalcoatl known as Ehecatl Quetzalcoatl -- an aspect of the god connected to the wind --, and is an aspect of Sak Nik (God H).
"South and Meso-American Mythology A to Z"; Ann Bingham, Jeremy Roberts; 2010
"A Dictionary of Non-Classical Mythology"; Lewis Spence; 2005
Missouri State University: MAYA GODS AND GODDESSES
University of Kansas: "Quetzalcoatl's Fathers A Critical Examination of Source Materials"; Brant Gardner; 1997