# Step 9 — Universal Commerce Protocol

/.well-known/ucp must answer 200 with protocol_version, services, capabilities, and endpoints — and a real version string, not a placeholder. Every spec URL and schema you reference has to be reachable, or the validator marks the field invalid.

Canonical: https://robauto.ai/learn/advanced-agentic-commerce/11

_Advanced Agentic Commerce: Ship the Full Agent Surface — lesson 11 of 20 (DEFINITION)_

/.well-known/ucp must answer 200 with protocol_version, services, capabilities, and endpoints — and a real version string, not a placeholder. Every spec URL and schema you reference has to be reachable, or the validator marks the field invalid.

Source: [UCP Specification](https://ucp.dev/specification/overview/?utm_source=robauto)

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Machine surfaces: https://robauto.ai/llms.txt · https://robauto.ai/llms-full.txt · https://robauto.ai/.well-known/api-catalog