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In a few minutes you’ll connect to ucp.trychannel3.com and search for products. No API key needed. Put your query in catalog. Curl examples also include "meta": null (why); the UCP CLI fills that in for you.

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Install UCP CLI

Channel3’s catalog works with @shopify/ucp-cli — Shopify’s reference CLI for UCP. Examples in this section show the same call as UCP CLI and curl so you can copy either one.
Channel3 is catalog-only (search, lookup, get product). Cart, checkout, and order commands in the CLI apply to other UCP merchants, not this endpoint.
On ucp.trychannel3.com, the CLI always uses the Anonymous tier. It does not send Channel3 API keys or UCP HTTP signatures. Use curl with an API key when you need Token-tier rate limits or affiliate variants[].url buy links tied to your vendor account.
npm install -g @shopify/ucp-cli
# or: npx @shopify/ucp-cli <command>
Prefer curl only? Skip install and use the curl tabs below.

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You’ll need

  • UCP CLI (installed above) or curl
  • Optional: API key for Token tier (curl only): higher limits and affiliate variants[].url buy links
Your agent runtime should point at https://ucp.trychannel3.com/mcp (Streamable HTTP MCP).

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1. Read the profile

ucp discover --business https://ucp.trychannel3.com --format json
This JSON lists the catalog tools and the MCP URL.

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2. Start an MCP session

# The CLI starts MCP sessions automatically on catalog commands.
ucp doctor
You should get a response that mentions channel3-catalog.

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3. Set your CLI profile

Point your local profile at the Channel3 catalog (discovery uses /.well-known/ucp on this host): 
ucp profile init --name channel3 --catalog https://ucp.trychannel3.com --activate
ucp profile show channel3 --format json
Confirm meta.defaults.catalog is https://ucp.trychannel3.com. If the profile already exists, add --force to re-point it (otherwise init is a no-op). After that, catalog commands can omit --business — they use meta.defaults.catalog from the profile. Override per shell if needed: 
export UCP_DEFAULT_CATALOG=https://ucp.trychannel3.com
Profile setup is CLI-only. Curl examples in this guide call ucp.trychannel3.com directly — no local profile needed.

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4. List tools

ucp catalog search --input-schema --format json
The curl tools/list returns all three tools: search_catalog, lookup_catalog, and get_product. The UCP CLI --input-schema shows the input schema for one tool (search_catalog here) — run ucp discover to see every negotiated tool. 
ucp catalog search \
  --set /query='running shoes' \
  --set '/pagination/limit=5' \
  --format json
In the response, open structuredContent (curl) or result (CLI):
  • products - the matches (title, price, store, variants)
  • pagination.cursor - copy this into the next request for page 2
  • pagination.has_next_page - true if there are more results

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What’s next

Add an API key

Token tier (curl): limits and monetizable links

Search in depth

Filters and pagination

Look up a store URL

Turn a product page link into catalog data

Rate limits

Anonymous vs API key