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1. Get an API key

Sign up at backside.app/signup to get your API key. Keys use the format: 
bsk_live_<43 alphanumeric characters>
Test keys use bsk_test_ prefix and hit isolated test data.
New tenants are automatically assigned the free trial tier. No Stripe Checkout is required to start using the API.
Your API key is shown once at creation. Store it securely — it cannot be retrieved again.

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2. Make your first request

curl https://api.backside.app/health

{ "status": "ok" }

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3. Authenticate

Pass your API key as a Bearer token: 
curl https://api.backside.app/api/v1/tenant \
  -H "Authorization: Bearer bsk_live_your_key_here"

{
  "id": "550e8400-e29b-41d4-a716-446655440000",
  "name": "My Company",
  "slug": "bks_a7f3k9m2p4x1",
  "plan": "free",
  "created_at": "2026-04-01T00:00:00Z"
}
The free plan is the auto-assigned trial tier. Upgrade to Pro or Scale via Stripe Checkout for higher rate limits.

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4. Create your first contact

curl -X POST https://api.backside.app/api/v1/contacts \
  -H "Authorization: Bearer bsk_live_your_key_here" \
  -H "Content-Type: application/json" \
  -d '{
    "display_name": "Jane Doe",
    "kind": "person"
  }'

{
  "id": "7a1b2c3d-4e5f-6789-abcd-ef0123456789",
  "tenant_id": "550e8400-e29b-41d4-a716-446655440000",
  "display_name": "Jane Doe",
  "kind": "person",
  "metadata": {},
  "created_at": "2026-04-01T12:00:00Z",
  "updated_at": "2026-04-01T12:00:00Z"
}

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5. Or pay per request (x402)

No API key needed. Pay with USDC on Base: 
curl https://api.backside.app/api/v1/contacts \
  -H "PAYMENT-SIGNATURE: <x402 receipt>"
See x402 payments for details.

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Next steps

Authentication

API keys, scopes, and the x402 payment path.

API Reference

Full endpoint documentation for all five domains.