How can I test embedded checkout experience

[subho-das]

I set up my embedded checkout endpoints already. Want to use the playground https://ucp.dev/playground/ to test the integration flow with my ucp.json. How can I paste the UCP.json. This page is non editable. Is there a way to test the embeded checkout experience?

[appdrops]

hi @subho-das, you might want to check out https://ucpplayground.com. It's a runtime built specifically for this use case: you can inspect your UCP manifest, test embedded checkout flows, and run real agents against your endpoints.

[subho-das]

@appdrops
How can I test the embedded checkout? I can see MCP and Rest is supported.

[appdrops]

Hey @subho-das — embedded checkout is fully supported! It triggers automatically when your checkout response returns status: "requires_escalation" with a continue_url.

Here's how to test it:

1. Select the EMBEDDED transport (or REST) in the playground
2. Search for a product and add it to cart
3. When your create_checkout response includes requires_escalation and a continue_url, the playground opens your checkout page in an iframe overlay
4. The ECP postMessage protocol handles the handshake (ec.ready → ec.start → ec.complete)

You can see a working example here: https://ucpplayground.com/playground?domain=https%3A%2F%2Fhouseofparfum.nl — they declare all three transports (MCP, REST, Embedded) and their checkout triggers the embedded overlay.

Your manifest declares embedded with a schema but no endpoint — that's fine, the checkout URL is provided dynamically. Just make sure your checkout API response includes those two fields and the overlay will trigger.

If you run into any other issues, just @ me here and I'll respond.