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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.
Without an API key, CLI catalog commands use the Anonymous tier. Pass --header "x-api-key: $CHANNEL3_API_KEY" per command, or add headers.json on your profile, for Token-tier rate limits and monetized buy links.
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: higher limits, monetized buy links, and optional placement commission data (authentication)
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

curl -sS https://ucp.trychannel3.com/.well-known/ucp | jq .
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

curl -sS -X POST https://ucp.trychannel3.com/mcp \
  -H 'Content-Type: application/json' \
  -H 'Accept: application/json, text/event-stream' \
  -d '{"jsonrpc":"2.0","id":1,"method":"initialize","params":{"protocolVersion":"2024-11-05","capabilities":{},"clientInfo":{"name":"my-agent","version":"1.0"}}}'
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

curl -sS -X POST https://ucp.trychannel3.com/mcp \
  -H 'Content-Type: application/json' \
  -H 'Accept: application/json, text/event-stream' \
  -d '{"jsonrpc":"2.0","id":2,"method":"tools/list","params":{}}'
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

curl -sS -X POST https://ucp.trychannel3.com/mcp \
  -H 'Content-Type: application/json' \
  -H 'Accept: application/json, text/event-stream' \
  -d '{
    "jsonrpc": "2.0",
    "id": 3,
    "method": "tools/call",
    "params": {
      "name": "search_catalog",
      "arguments": {
        "meta": null,
        "catalog": {
          "query": "running shoes",
          "pagination": { "limit": 5 }
        }
      }
    }
  }'
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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6. Search with your API key

For production traffic, create a key and send it on every catalog call. Channel3 accepts x-api-key or Authorization: Bearer <key>. 
export CHANNEL3_API_KEY="ch3_live_..."

ucp catalog search \
  --header "x-api-key: $CHANNEL3_API_KEY" \
  --set /query='running shoes' \
  --set '/pagination/limit=5' \
  --format json

curl -sS -D - -o /tmp/ucp-search.json -X POST https://ucp.trychannel3.com/mcp \
  -H 'Content-Type: application/json' \
  -H 'Accept: application/json, text/event-stream' \
  -H "x-api-key: $CHANNEL3_API_KEY" \
  -d '{
    "jsonrpc": "2.0",
    "id": 4,
    "method": "tools/call",
    "params": {
      "name": "search_catalog",
      "arguments": {
        "meta": null,
        "catalog": {
          "query": "running shoes",
          "pagination": { "limit": 5 }
        }
      }
    }
  }'
Confirm Token tier in the response headers: 
x-ucp-auth-tier: token
Your buy links should be monetized to your account. Compare with step 5 without a key (no monetization).

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Placement commission data (optional)

The API key alone attributes buy links to your account. To also receive variants[].placement commission percentages, opt in with catalog.placements: ["affiliate"]. Without a Token-tier key, placements are never returned even if you pass the field. 
ucp catalog search \
  --header "x-api-key: $CHANNEL3_API_KEY" \
  --set /query='running shoes' \
  --set '/pagination/limit=5' \
  --set '/placements=["affiliate"]' \
  --format json

curl -sS -X POST https://ucp.trychannel3.com/mcp \
  -H 'Content-Type: application/json' \
  -H 'Accept: application/json, text/event-stream' \
  -H "x-api-key: $CHANNEL3_API_KEY" \
  -d '{
    "jsonrpc": "2.0",
    "id": 5,
    "method": "tools/call",
    "params": {
      "name": "search_catalog",
      "arguments": {
        "meta": null,
        "catalog": {
          "query": "running shoes",
          "pagination": { "limit": 5 },
          "placements": ["affiliate"]
        }
      }
    }
  }'
On monetizable offers, matching variants include placement with the commission rate (e.g. 12.5 = 12.5%). Omitted placement means no disclosed commission for that offer — not zero. See Extension reference.
Add ~/.ucp/profiles/channel3/headers.json so the key is sent automatically:
{
  "default": {},
  "businesses": {
    "https://ucp.trychannel3.com": {
      "x-api-key": "${CHANNEL3_API_KEY}"
    }
  }
}
Keep CHANNEL3_API_KEY in your shell environment. See Authentication for placements and more detail.

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What’s next

Authentication

Placements, persistent headers, Bearer auth

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