YieldSignal

Real-time, risk-weighted USDC and WETH lending APY across Aave, Compound, Morpho, Moonwell, Euler and Fluid on Base — paid per call via x402.

$0.01/call3 free/day per IP via ?trial=1no API key

REST

GET https://yieldsignal.vercel.app/signal/usdc-base-yield
GET https://yieldsignal.vercel.app/signal/weth-base-yield

Call it without payment and you'll get a 402 Payment Required with the exact price/asset/network. Any x402-compatible client (e.g. @x402/fetch) completes the payment automatically. Add ?trial=1 to use one of the 3 free daily calls per IP instead of paying.

MCP

POST https://yieldsignal.vercel.app/mcp

Tool get_yield_signal (optional asset: "USDC" or "WETH", defaults to USDC), gated per-call via @x402/mcp — tools/list/initialize stay free, only the tool call is paid.

Every reading is source-tagged

{
  "asset": "USDC",
  "bestProtocol": "compound",
  "gapBps": 57,
  "rates": [
    { "protocol": "compound", "apyBps": 490, "weightedApyBps": 485, "source": "onchain", "asOf": "..." },
    { "protocol": "moonwell", "apyBps": 440, "weightedApyBps": 387, "source": "defillama", "asOf": "..." }
  ]
}

source is onchain/api (read directly from the protocol — Aave, Compound and Morpho) or defillama (aggregator — Moonwell, Euler and Fluid) — a reading that fails or looks invalid is omitted, never estimated.

Verifiable, not just claimed

Two independent ways to check a response wasn't tampered with or fabricated, without needing to trust our uptime at query time:

• Signed responses — every REST/MCP response is signed (EIP-191 personal_sign) by the same payTo address the 402 payment requirement names for that route. REST exposes it as X-Signal-Signature/X-Signal-Signer response headers over the exact response body; MCP returns it as a sibling content block over the exact previous block's text. Verify with viem's verifyMessage.
• On-chain attestations (EAS, Base mainnet) — periodic public, permanent records of "at time T, protocol X paid Y bps, Z ahead of the runner-up," independently verifiable on easscan.org without trusting this server at all. Attester address is that same payTo address. Published automatically whenever the signal changes materially or gets stale (not on every call — see track record).

Agent discovery & reputation

Registration file (ERC-8004) at /agent-card.json — a portable identity for this service, discoverable outside x402-specific directories. Once registered on-chain (IdentityRegistry), any buyer can leave verifiable feedback via the ReputationRegistry — see the agent card for both contract addresses.