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You can use the catalog with no login (Anonymous tier). Without a key, requests run as Anonymous: lower rate limits and no monetization. For production, add a Channel3 API key for the Token tier: higher rate limits, monetization on variants[].url buy links, and optional placement commission data when you opt in.

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1. Create a key

  1. Go to the dashboard.
  2. Create an API key.
  3. Keep it out of git:
export CHANNEL3_API_KEY="ch3_live_..."

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2. Send it on every MCP request

Channel3 accepts x-api-key or Authorization: Bearer <key> on each POST to /mcp. 
# Per command — repeat --header on every catalog call
ucp catalog search \
  --profile channel3 \
  --header "x-api-key: $CHANNEL3_API_KEY" \
  --set /query='wireless headphones' \
  --set '/pagination/limit=3' \
  --format json

# ~/.ucp/profiles/channel3/headers.json
{
  "default": {},
  "businesses": {
    "https://ucp.trychannel3.com": {
      "x-api-key": "${CHANNEL3_API_KEY}"
    }
  }
}

# Then export CHANNEL3_API_KEY in your shell; all catalog commands use Token tier.
ucp catalog search \
  --set /query='wireless headphones' \
  --set '/pagination/limit=3' \
  --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": 1,
    "method": "tools/call",
    "params": {
      "name": "search_catalog",
      "arguments": {
        "meta": null,
        "catalog": {
          "query": "wireless headphones",
          "pagination": { "limit": 3 }
        }
      }
    }
  }'
The UCP CLI has no separate --api-key flag. Use --header per call or headers.json on the profile (Shopify ucp-cli docs). Values support ${ENV_VAR} interpolation so secrets stay out of the file.

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3. Request placement commission data (optional)

With a Token-tier key, add catalog.placements: ["affiliate"] to receive variants[].placement commission data. See Extension reference. 
ucp catalog search \
  --header "x-api-key: $CHANNEL3_API_KEY" \
  --set /query='running shoes' \
  --set '/placements=["affiliate"]' \
  --format json

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4. Check that it worked

Response headers: 
x-ucp-auth-tier: token
In structuredContent (curl) or result (CLI), your buy links should be monetized to your account. Compare with the same search without a key (no monetization). Bad or missing keys fall back to anonymous limits (no 401): 
x-ucp-auth-tier: anonymous

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What’s next

Rate limits

Anonymous vs Token

Search

Run a search with your key