Is there a document describing how the protocol work?

I am reading the source code of counterpartyd, and in the config.py ,there is a const
"

    # Counterparty protocol
    TXTYPE_FORMAT = ‘>I’


"
I assume the ‘>I’ is a part of “Counterparty protocol”, but where is the document of “Counterparty protocol” ?
Surely it doesn’t mean that I have to summarize the protocol by reading the code?

The best place is the specs at https://github.com/CounterpartyXCP/Counterparty


as far as the bitpacking is concerned, the code is the "reference" here.