Options venues impose limits: a maximum number of contracts per strike or expiry, a cap on total notional, and sometimes limits on aggregate exposure to a single Greek.
They exist because the venue must be able to manage the position if something goes wrong — the same logic behind leverage tiers on perpetuals.
Why they are informative
Limits are set against how much the venue believes a book can absorb. A generous cap on BTC and a tight one on a newly listed altcoin is the venue stating, in public, that the second book is thin.
That is a free liquidity read requiring no data at all, and it is a useful cross-check on figures computed from a thin book that look more solid than they are.
What they mean in practice
For most retail positions, nothing — the caps sit well above ordinary size. Where they bite is on anyone trying to express a large view in a small book, which is precisely the case where the position would be hard to exit anyway.
So the limit is usually enforcing a constraint the market would have enforced through execution cost regardless.
The knock-on for the dealer map
Limits bound how concentrated open interest at a single strike can become, which puts a ceiling on how large a wall any one participant can create — a partial mitigation of the block trade problem, though a high one.
The check
Read the limits table alongside the contract specification, once per venue and per coin. It takes a minute and tells you what the venue thinks of the book before you compute anything from it.