git:20260309.786511c to git:20260914.08f85a3

9 added, 8 removed. Audit A to A.

---

name: ap2-mcp-server

description: Implement AP2 MCP servers — payment tools exposed via Model Context Protocol for agent access to payment capabilities. Use when building MCP-based payment tool integrations for AP2.

allowed-tools: Read, Write, Edit, Bash, Grep, Glob, WebSearch, WebFetch

---

# AP2 MCP Server Integration

## Before writing code

**Fetch live docs**:

- 1. Fetch `https://ap2-protocol.org/specification/` for MCP server references

- 2. Fetch `https://ap2-protocol.org/topics/ap2-a2a-and-mcp/` for MCP integration details

- 3. Fetch `https://ap2-protocol.org/roadmap/` to check MCP server availability status

+ 1. Fetch `https://ap2-protocol.org/ap2/specification/` for MCP server references

+ 2. Fetch `https://ap2-protocol.org/ap2/implementation_considerations/` for MCP integration details

+ 3. Fetch `https://github.com/google-agentic-commerce/AP2/releases` to check MCP server availability status

4. Web-search `site:github.com google-agentic-commerce AP2 MCP server` for MCP implementations

## Conceptual Architecture

### AP2 + MCP

While AP2's primary integration is with A2A (agent-to-agent), it also integrates with **MCP (Model Context Protocol)** for tool-based access to payment capabilities:

- **A2A** — Agent-to-agent: Shopping Agent ↔ Merchant Agent communication

- **MCP** — Agent-to-tool: Agent accessing payment APIs as tools

### MCP's Role in the Stack

MCP provides the foundational layer for connecting agents to external resources:

```

Agent

├── A2A → Other Agents (Merchant, CP, MPP)

└── MCP → Payment Tools (APIs, databases, services)

```

### AP2 MCP Server

The AP2 MCP server exposes payment-related tools that agents can call:

- Payment method management tools

- Mandate creation and signing tools

- Transaction status tools

- Receipt retrieval tools

### Roadmap Status

- The AP2 roadmap includes:

- - **V0.1**: A2A extension (primary), MCP server v0.1

- - **V1.x**: MCP-based implementation sequence diagrams, expanded MCP support

+ AP2's primary binding has been the **A2A extension**, with MCP support arriving alongside it and expanding over time. Since the protocol moved to the FIDO Alliance for community governance, the roadmap is set there rather than in a single vendor repo.

- Check the latest roadmap and GitHub for current MCP server availability.

+ **Resolve the current state before building** — do not assume the split above still holds:

+ - Check the AP2 repo's `CHANGELOG.md` and `code/` for what the MCP surface actually exposes today.

+ - Check FIDO Alliance working-group output (Agentic Authentication TWG, Payments TWG) for where the standard is heading.

+ - Confirm which binding — A2A extension or MCP — is the supported path for your integration.

### MCP Tool Patterns for Payments

> **Note**: The following tool names are entirely **speculative/hypothetical examples** illustrating what an AP2 MCP server might expose. They are **not from any published AP2 MCP server specification or implementation**. Always check the latest AP2 roadmap and GitHub repositories for actual MCP tool definitions.

Hypothetical AP2 MCP tools:

| Tool | Description |

|------|-------------|

| `list_payment_methods` | Get available payment methods for a user |

| `create_intent_mandate` | Build an Intent Mandate from shopping parameters |

- | `create_cart_mandate` | Build a Cart Mandate from product/price details |

+ | `create_cart_mandate` | Build a Checkout Mandate from product/price details |

| `validate_mandate` | Verify mandate signatures and contents |

| `process_payment` | Submit a payment for processing |

| `get_transaction_status` | Check payment processing status |

| `get_receipt` | Retrieve a payment receipt |

### When to Use MCP vs A2A for Payments

| Scenario | Use |

|----------|-----|

| Agent calling another agent (Merchant, CP) | A2A |

| Agent calling a payment API/tool directly | MCP |

| Multi-step agent negotiation | A2A |

| Simple payment status check | MCP |

| Complex multi-party flow | A2A |

| Tool-based payment method query | MCP |

### Integration Architecture

```

Shopping Agent

├── A2A → Merchant Agent

├── A2A → Credentials Provider Agent

├── MCP → Payment Tools Server

└── MCP → Product Catalog Server

```

### Best Practices

- Use A2A for multi-party payment flows (the primary AP2 pattern)

- Use MCP for single-call tool operations (status checks, receipts)

- Don't expose raw payment credentials through MCP tools

- Follow the same security model (VDCs, signing) regardless of transport

- Check the roadmap for MCP server maturity before relying on it

- Test MCP tools alongside A2A flows for consistency

Fetch the latest roadmap and any published MCP server implementations for exact tool schemas and availability before implementing.