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A profile is a small JSON file at a fixed URL. Agents read it to learn which UCP features a server supports.

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Channel3’s profile

GET https://ucp.trychannel3.com/.well-known/ucp
Fetch this once when your agent starts (or cache it for a few hours). It advertises catalog search and lookup, the MCP URL, and the com.trychannel3.catalog.global extension.

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Do you need your own profile?

No. In full UCP, a merchant might host a profile for cart, checkout, and orders. Channel3’s catalog is search and lookup only — you consume Channel3’s profile; you don’t publish one. Auth is separate. Identifying yourself to Channel3 uses an optional API key in HTTP headers, not a profile file. See Authentication and Rate limits.

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What is meta?

UCP tool calls look like { "meta": ..., "catalog": ... }. Put your query in catalog (query, ids, urls, filters, pagination). meta is for capability negotiation in the UCP spec. On ucp.trychannel3.com today, catalog tools ignore it — pass "meta": null in curl. Auth uses HTTP headers (x-api-key), not meta.

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What’s next

API key

Token tier setup

Rate limits

Anonymous vs Token