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name: UCP Protocol Architecture description: This skill should be used when the user asks about "UCP architecture", "protocol structure", "OpenAPI spec", "OpenRPC spec", "capability design", "method naming", or needs to understand how UCP works. Provides guidance on UCP's layered architecture and spec generation. version: 1.0.0

UCP Protocol Architecture

Overview

Universal Commerce Protocol (UCP) is an open standard for commerce interoperability. It enables AI agents and applications to interact with e-commerce systems through a unified API specification.

Protocol Layers

Copy┌─────────────────────────────────────────┐
│           Generated Specs               │
│  (OpenAPI 3.1.0 + OpenRPC 1.3.2)       │
├─────────────────────────────────────────┤
│           Source Schemas                │
│      (JSON Schema Draft 2020-12)        │
├─────────────────────────────────────────┤
│          Type Definitions               │
│      (Reusable Commerce Types)          │
└─────────────────────────────────────────┘

Directory Structure

Copyucp/
├── source/
│   └── schemas/
│       └── shopping/           # Source JSON schemas
│           ├── checkout.json
│           ├── order.json
│           ├── payment.json
│           ├── product.json
│           ├── cart.json
│           ├── customer.json
│           ├── fulfillment.json
│           └── types/          # Reusable types
├── generated/
│   ├── openapi/               # OpenAPI 3.1.0 specs
│   │   └── shopping.openapi.json
│   ├── openrpc/               # OpenRPC 1.3.2 specs
│   │   └── shopping.openrpc.json
│   └── json-schema/           # Bundled schemas
│       └── shopping.schema.json
├── scripts/
│   ├── generate_schemas.py    # Main generation script
│   ├── validate_specs.py      # Validation script
│   └── generate_ts_schema_types.js
└── docs/                      # Documentation

Method Naming Convention

UCP methods follow dot notation: domain.capability.action

Examples:

• shopping.cart.create - Create a cart
• shopping.cart.add_item - Add item to cart
• shopping.checkout.initiate - Start checkout
• shopping.order.get - Get order details
• shopping.product.search - Search products

Generation Pipeline

Source schemas are processed to generate:

1. OpenAPI 3.1.0 - REST API specification
2. OpenRPC 1.3.2 - JSON-RPC specification
3. Bundled JSON Schema - Dereferenced schemas
4. TypeScript Types - Type definitions

Running Generation

Copy# Generate all specs
python scripts/generate_schemas.py

# Generate TypeScript types
node scripts/generate_ts_schema_types.js

Validation Pipeline

Validation ensures schema correctness:

Copy# Validate all specs
python scripts/validate_specs.py

Validation checks:

• JSON Schema syntax valid
• All $ref references resolve
• UCP annotations present
• Method names follow convention
• Required fields defined

Capability Design Process

To add a new capability:

1. Design types - Create reusable types in types/
2. Define schemas - Create capability schema with request/response
3. Add annotations - Apply ucp_request/ucp_response
4. Validate - Run validate_specs.py
5. Generate - Run generate_schemas.py
6. Review - Check generated OpenAPI/OpenRPC

Core vs Capability Schemas

Core schemas (ucp_core: true):

• Protocol-level fields
• Error handling
• Pagination
• Common metadata

Capability schemas:

• Domain-specific operations
• Business logic
• Commerce entities

Additional Resources

Reference Files

For detailed architecture documentation:

• references/openapi-patterns.md - OpenAPI generation patterns
• references/openrpc-patterns.md - OpenRPC generation patterns

Examples

• examples/full-capability-flow.md - End-to-end capability creation
• examples/method-naming.md - Method naming examples