Agent checkout

Coming next. REST, the MCP server and HTTP 402 are being built in waves T1 and T2.

Planned. AP2 mandates and ACP checkout endpoints follow in wave T7.

The flow is the same over every protocol:

1. Quote. The seller agent returns a price.
2. Cart. The buyer agent confirms what it is buying.
3. Pay. TatvaPay checks the buyer's mandate and the risk rules, then instructs the partner rail.
4. Receipt. Both sides get a signed, hash-chained receipt.

Every step is idempotent: send an Idempotency-Key with each request.