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+# st0x Server API Specification V1
+
+## Goal
+
+Provide signed price quotes for specific trading pairs that can be used by solvers in Raindex orders. Each endpoint handles a single trading pair and returns a signed context containing quote information.
+
+## Magic Numbers
+
+- Web data metadata magic number: `0xff5dcce9b571ba42`
+- st0x API magic number: `0xfff5093d312bd907` (first 7 bytes of keccak256("st0xpair") prepended with 0xff)
+
+## Server Advertisement
+
+Servers advertise price quote endpoints on metaboard with:
+- 8 byte magic number for st0x API
+- Remaining bytes contain UTF-8 encoded URL where the API is hosted for a specific trading pair
+
+Each trading pair requires its own advertisement. Orders reference these advertisements by their hash to save gas.
+
+## Request Format
+
+Clients (solvers) then POST raw octet streams to the server URL according to the Web Data V1 specification, where the hash is from the server advertisement on the metaboard.
+
+No additional payload is needed, since each endpoint is pair-specific.
+
+## Server Response
+
+The server returns a SignedContextV1 structure containing:
+
+```solidity
+struct SignedContextV1 {
+    address signer;           // Account that signed the context
+    uint256[] context;        // The signed data array
+    bytes signature;          // EIP-1271 compliant signature
+}
+```
+
+The `context` array contains:
+```
+[
+    uint256 ioRatio,        // Price ratio for the trading pair in 18 fixed point decimal
+    uint256 input,          // ABI encoded address of the input token (ie padded to 32 bytes)
+    uint256 output,         // ABI encoded address of the output token (ie padded to 32 bytes)
+    uint256 expiry,         // Timestamp in seconds when quote expires
+    uint256 chainId,        // Chain ID of the chain the quote is valid on
+    
+]
+```
+
+The signature MUST be over the ABI packed encoded bytes of the context array (concatenated without length prefix), hashed, and handled per EIP-191.
+
+## Server Requirements
+
+The server MUST:
+1. Validate the signature
+2. Verify the web data hash matches its own advertisement for this specific pair
+3. Check timestamp is not expired
+4. Ensure nonce hasn't been used in a non-expired request
+5. Only accept requests if the signing key has a nonzero L1 balance (optional anti-sybil measure)
+
+## Client Usage
+
+1. Solver retrieves the signed context from the appropriate pair endpoint
+2. Solver provides the signed context to Raindex orders during take/clear operations
+3. The order can then validate and use the quote information according to its logic:
+   - Verify quote hasn't expired
+   - Check validFrom time has passed
+   - Validate pair hash matches expected pair
+   - Use ioRatio for price calculations
+
+## Security Considerations
+
+- Each endpoint serves a single pair to reduce complexity
+- All quotes include validity timeframes
+- Binary format reduces attack surface
+- Hash references save gas
+- Nonces prevent replay attacks
+- Optional L1 balance checks can prevent sybil attacks
+- Support for both EOA and EIP-1271 contract signatures
+- Contract signatures can be revoked at any time
+
+## Extensions
+
+The protocol intentionally omits:
+- Complex order types
+- Multi-pair quotes
+- Account management
+- Complex rate limiting
+
+Orders implement their own logic for using the quote data.
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