Not every AI agent needs the same payment protocol. A2A bank transfers, card mandates, and HTTP-native x402 flows each have distinct protocol stacks, consent models, and MCP integration patterns. Pick your scenario below — the four-tool chain adjusts to show you exactly what to evaluate, build, and validate.
Each scenario loads the same four-tool chain with different emphasis — step 2 and step 3 swap to the protocol tools most relevant to your use case.
Before committing to a protocol stack, compare how AP2, the Agentic Commerce Protocol (ACP / Shared Payment Token), x402, Visa Trusted Agent Protocol, and Mastercard Agent Pay differ on consent model, token scope, settlement rail, and MCP integration requirements. The field crosswalk maps every parameter across protocols so you can see where they overlap and where they diverge for your use case.
Build and validate a Google AP2 Checkout or Payment Mandate Verifiable Digital Credential (VDC) for your A2A corridor. AP2 mandates define the agent's authorisation scope — payment method, amount limits, expiry, and the specific rails the agent may use. The validator checks your mandate against the AP2 Open and Closed Wallet schemas before you hand it off to the agent runtime.
Once your A2A mandate is built, validate the Agent Card that advertises your agent's payment capabilities to other agents and orchestrators. The Agent Card is how the Google A2A protocol discovers what payment actions your agent can perform — a malformed card means the agent is invisible to orchestration layers. This tool validates the card schema, checks extension fields, and flags missing capability declarations.
Before your agent goes to production, score the MCP server that exposes your payment tools. The scorecard rolls up tool-definition quality, server.json registry-readiness, OAuth 2.1 posture, transport security, tool-poisoning hygiene, and spec-revision compliance into a graded report. Regardless of which payment protocol you chose in Steps 1–3, this is the gate that determines whether the MCP layer around your agent is production-safe.
After running this chain you will have: a protocol recommendation grounded in your specific rail requirements (T276), a validated mandate or token definition for your chosen protocol (Step 2), a rail-specific compliance artefact ready for the agent runtime (Step 3), and an MCP server readiness score that tells you whether the infrastructure around your agent is production-safe (T288).
The AP2 JSON export from T288 can be ingested directly by an MCP agent runtime as a structured compliance record — closing the loop from protocol selection through to agent deployment.