Correct field name for max pledge made?

I’ve found two: pledge_cap_cents and pledge_cap_amount_cents but neither work.

Both return:

{
	"errors": [
		{
			"code": 1,
			"code_name": "ParameterInvalidOnType",
			"detail": "Invalid parameter for 'fields[member]' on type member: ['pledge_cap_amount_cents'].",
			"status": "400",
			"title": "Invalid value for parameter 'fields[member]'."
		}
	]
}

I need to know the max pledge a patron has made!

I dont think either of those represents the max ever pledge paid. You will likely have to go through the patron’s pledge history and check for the highest pledge payment.