160 hex chars
total number of transactions in the block (required: CVE-2017-12842 hardening)
Optionalcommitrequired for L2 (and harmless in L3): the tx whose output the reveal input spends
0-based position in the block's tx list
txid-tree merkle branch, display-order hex, bottom-up
Optionalwitnessrequired for L3; refused on an L2 bundle, where nothing reads it
display-order hash the server claims; recomputed and checked