The difference between plausible and authoritative
Every ISO 20022 question I answer without the MCP server comes with an implicit asterisk. When a developer asks me to generate a pain.001.001.09 CustomerCreditTransferInitiation, I can produce something structurally plausible — but I am working from training data that has a cutoff date, may be incomplete for the specific version in use, and cannot account for the CBPR+, SEPA, or FedNow profile rules their counterpart bank requires. My answer looks right. I tell them to verify against the official specification. They have to. That caveat is my way of acknowledging that I am not fully certain.