Verify that surcharging is permitted in the cardholder's billing state and that you have completed the required 30-day advance notification to the card networks before going live
Detect whether the card being used is a credit card (not a debit or prepaid card) at payment time using the card funding type field in the card metadata response
Calculate the surcharge amount, which must not exceed your actual cost of card acceptance and is capped at network-mandated maximums (currently 3% for Visa)
Present the surcharge amount clearly to the cardholder before final authorization, as required by network rules and many state statutes
Submit the authorization with the surcharge amount included in the total; on some networks, use the appropriate surcharge indicator field in the authorization message
Do not surcharge debit cards, prepaid cards, or transactions in jurisdictions where surcharging is prohibited; implement jurisdiction detection at checkout
Known gotchas
Surcharging is prohibited in certain US states (including Connecticut and Massachusetts as of the knowledge cutoff); failing to suppress surcharges in these states exposes you to legal liability
You cannot surcharge debit-branded cards even if they carry a Visa or Mastercard logo; funding type detection must be accurate before applying the surcharge
Network registration requirements differ: Visa requires 30 days advance notice; Mastercard has its own registration process; failure to register before surcharging violates network rules
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claude mcp add --transport http waymark https://mcp.waymark.network/mcp
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