 Scoped virtual cards external agents can spend within company policy, plus an MCP server over spend data MCPOpenAPI | virtual-cards+4 | MCP+1 | MPP | m2m-oauth, Payments | 4/5 | | |
 KYA agent identity plus wallets and pay-per-call settlement so services can charge unknown agents safely MCPOpenAPIllms.txt | agent-identity+4 | MCP+2 | x402 | wallet, Payments | 4/5 | | |
 Payments-focused L1 built for machine payments, co-author of MPP and home of the MPP service directory MCPOpenAPIllms.txt | mpp+4 | MCP+2 | MPP | wallet, Payments | 4/5 | | |
 Network tokens and credentials for approved agents, plus one endpoint bridging TAP, MPP, ACP and UCP OpenAPI | bridge+7 | OpenAPI | MPP+5 | api-key, Payments | 4/5 | | |
 Open framework using HTTP Message Signatures (RFC 9421) so merchants can recognize and trust a legitimate agent before it transacts OpenAPI | tap+4 | OpenAPI | TAP | none, Payments | 4/5 | | |
 API gateway that puts an x402 or key-based paywall in front of any endpoint agents call MCPOpenAPIllms.txt | api-gateway+4 | MCP+2 | x402 | api-key, Payments | 4/5 | | |
 Alibaba and Ant International trust protocol for agent commerce, running at scale across Asian marketplaces | actp+4 | — | ACTP | api-key, Payments | 3/5 | | |
 Amex developer kit for agent-initiated card payments with cardholder-scoped authorization OpenAPI | ace+3 | OpenAPI | ACE | api-key, Payments | 3/5 | | |
 Accept stablecoin and crypto payments through a hosted checkout API OpenAPI | payments+3 | OpenAPI | — | api-key, Payments | 3/5 | | |
 Wallet and mandate infrastructure for agentic checkout, aligned to ACP flows OpenAPI | agent-wallets+3 | OpenAPI | ACP | api-key, Payments | 3/5 | | |
 Crypto payment gateway API supporting 300+ assets with webhooks and payouts OpenAPIllms.txt | payments+3 | OpenAPI+1 | — | api-key, Payments | 3/5 | | |
 Human-in-the-loop payment rails that let agents move real money under explicit approval policies OpenAPI | agent-payments+3 | OpenAPI | — | api-key, Payments | 3/5 | | |
 Programmatic virtual card issuing with agent-compatible APIs and granular spend rules OpenAPIllms.txt | virtual-cards+3 | OpenAPI+1 | — | api-key, Payments | 3/5 | | |