Add agent discovery support for @emdash-cms/x402 so EmDash sites can be found and fetched by AI agents

[fmhall]

Summary

I’d like EmDash’s @emdash-cms/x402 integration to support agent-friendly discovery metadata so AI agents can find paid resources on an EmDash-powered site, understand how to call them, and pay automatically when appropriate.

The core idea is to let a site expose a machine-readable discovery document, an openapi.json, which fits the agent discovery standard from Merit Systems and used by agents through AgentCash. This discovery standard was built in collaboration with Coinbase and Stripe/Tempo. Full spec can be found here.

It's a standard openapi.json, but includes a few extra fields specific to agent discovery and payment.

EmDash is well-positioned for this

EmDash already has strong CMS and content modeling primitives, and @emdash-cms/x402 already handles enforcement. Discovery through the bazaar is supported, but insufficient for agents to find and pay for resources programmatically without running their own x402 infrastructure.

Adding discovery is a natural extension:

• enforcement already exists
• the missing piece is discoverability
• OpenAPI is already a familiar ecosystem standard

Why now

Agents are increasingly using structured API discovery instead of ad hoc browsing. EmDash already has the enforcement half of the story through x402. Adding discovery closes the loop and makes the feature materially useful in real agent workflows.

[fmhall]

Would appreciate any feedback here, I've also started work on a draft PR I can share if interest!