Set Campaign Budget

Sets a campaign's daily budget. Safety limits: a single increase above +50% is blocked, the TOTAL increase within 24h may not exceed +100% of the budget at the start of that window, and a single cut deeper than -80% is blocked — pause the campaign instead.

There is also an absolute floor, about 5 USD per day converted into the account's currency, because a budget pulled down to near zero stops delivery while the campaign still reads as active in the interface — an invisible way to kill a campaign. A small local campaign can legitimately sit below that floor, so `allow_low_budget=true` clears it: the flag makes the decision explicit rather than accidental. Say plainly that delivery may be thin or stop at that level, and check the bid — a daily budget below one click's worth of max CPC buys nothing. Everything else (the increase caps, the -80% rule) still applies. If confirm=false, returns a dry-run preview.