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The standard ACP feed at /feed/acp.json is open and free — every catalog item Droplinked exposes to agentic shoppers lives there. The premium feed at /feed/acp.premium.json returns a richer, ranked, agent-tuned slice of the same inventory (higher refresh cadence, attribution-weighted ordering, more granular merchant signals) — and it is gated by the x402 HTTP 402 micropayment protocol. The price is intentionally per-call rather than per-subscription so an autonomous agent can pull the feed on demand without operating a Droplinked subscription.

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At a glance

EndpointGET https://apiv3.droplinked.com/feed/acp.premium.json
Protocolx402 — 402 Payment Required per call
SettlementUSDC on Base mainnet
Price per call$0.001 (1,000 atomic USDC units, 6 decimals)
Facilitatorhttps://x402.org/facilitator (Coinbase canonical)
PayTo0xB2721aD74B8E88F8c31f61c88c42b41468f5ba28 (Droplinked treasury)
Asset0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 (Circle USDC on Base)

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The protocol in three round-trips

1. Agent: GET /feed/acp.premium.json                       (no payment)
   Droplinked: 402 Payment Required
   Body: {
     "scheme":   "exact",
     "network":  "base",
     "maxAmountRequired": "1000",
     "asset":    "0x833589f…",
     "payTo":    "0xB2721aD7…",
     "resource": "https://apiv3.droplinked.com/feed/acp.premium.json",
     "extra":    { "currency": "USDC" }
   }

2. Agent (off-protocol): signs a USDC transfer for 1,000 atomic units to `payTo`
                          on Base mainnet, gets back a payment proof.

3. Agent: GET /feed/acp.premium.json
          Header: X-PAYMENT: <serialised proof>
   Droplinked: facilitator verifies proof → 200 OK + JSON feed body
The first call always returns 402 — there is no API key authentication. Every authorised caller is identified by a signed payment proof.

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How agents typically integrate this

Most agent SDKs that target Coinbase / Anthropic / OpenAI surfaces ship with x402 support out of the box. The pattern is:
  1. The agent has a CDP (Coinbase Developer Platform) wallet or another EIP-1559 wallet with USDC on Base.
  2. The wallet is configured with a per-request signing budget (e.g. “spend up to $1 USDC per minute on x402-gated endpoints”).
  3. The agent’s HTTP client transparently retries the second-round GET with the X-PAYMENT header when it sees a 402, using cached proofs to avoid re-signing within a quote window.
If you’re building an agent without SDK support, you can implement the full handshake by reading the x402 protocol spec.

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What’s in the premium feed

The premium feed body is shape-compatible with /feed/acp.json so agents that already consume the open feed can swap endpoints. The differences:
  • Refresh cadence: ~5 minutes (open feed is hourly)
  • Ranking: attribution-weighted — merchants with verified KYB (verifiedTier: "full"), active EAS Schema A chain, and >$10K monthly agentic GMV bubble up
  • Granular signals: each catalog row carries discoveryRank, verifiedTier, monthlyAgenticGmvBucket, and lastSettledOrderAt
  • No throttling: the open feed limits requests per IP; the premium feed has no IP-based throttle since each call is paid

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Calibration window (current)

The premium feed is live on production as of 2026-06-15 02:18Z. Per Droplinked operator decision #2097, on-chain USDC settlement against the treasury wallet starts firing once the trailing-30-day accrual log crosses $1,000 USDC pending. Until then, the protocol captures + verifies payments via the facilitator but routes the settlement event to the internal accrual log (AffiliatePayoutAccrual) rather than to an on-chain transfer. This is a deliberate ramp: the protocol gating is real (agents must sign and present proofs), but the settlement-to-treasury leg flips when the volume justifies on-chain gas. Operators can verify the current accrual state via the SuperAdmin dashboard at https://admin.droplinked.com/monetization/x402-earnings.

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Failure modes

HTTP statusReason
402First call — present a signed payment proof in X-PAYMENT and retry.
503 X402_NOT_CONFIGUREDOperator has not set X402_FACILITATOR_URL. Surface to operator, do not retry.
503 X402_FACILITATOR_UNAVAILABLEFacilitator circuit breaker is OPEN. Retry with exponential backoff.
4xx after X-PAYMENTPayment proof rejected — re-sign with a fresh nonce.
200 OKBody is the premium feed JSON.

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Why x402 (and not API keys)

x402 was chosen over API keys for the same reason Droplinked is built on EAS attestations: the buyer/agent identity is the cryptographic signature, not a long-lived shared secret held by an account team. There’s no key to rotate, no key to leak, no quota to provision. An agent operator pays for the calls they actually make, settles in USDC on-chain, and gets no recurring bill. The trade-off is that agent wallets need USDC on Base ($0.001 per call is trivial but non-zero), and the protocol is younger than HTTP Basic. Both gaps are being closed by the broader x402 ecosystem — Storyflo’s get_premium_briefing MCP tool uses the exact same facilitator and settlement pattern as a reference integration.