A posting's amount is VAT-inclusive on SALE and REFUND entries and VAT-exclusive on REVENUE_RECOGNITION and REVENUE_RECOGNITION_REVERSAL entries. Both carry a vat_rate, so the rate alone does not tell you which you are holding — the entry's kind does.
This matters most when the destination system splits VAT for you. Handing it a net recognition amount together with a rate makes it strip VAT that was never in the amount, which understates revenue and leaves the prepayment short by the difference. See amount and vat_rate on a posting for the full rules.
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