I have a wager that 'pooped' in "I am pooped" is not an adjective; however the betting party contends that it is an adjective since "it describes the state of the subject, I".

The other party also cites the wictionary entry for pooped as evidence.

I have found evidence that pooped is used as a verb, such as this CMU automated grammar parser; however the grammar parser concedes it is guessing at the part of speech (note the [!]) in the output...

++++Time                                          0.00 seconds (59.77 total)
Found 1 linkage (1 with no P.P. violations)
  Unique linkage. cost vector = (UNUSED=0 DIS=0 AND=0 LEN=3)

 +-SX-+---Pv--+
 |    |       |
I.p am.v pooped[!].v 

Constituent tree:

(S (NP I)
   (VP am
       (VP pooped)))

Could someone explain the part of speech that 'pooped' is above, as well as the rationale for choosing this response?