Rain

Step zero — from nothing to your first trade

1. Create the account. Start at the venue’s site and connect an Arbitrum EOA. The repository sources do not establish whether Rain registration is required or what identity check applies, so verify that prerequisite with the venue.
2. Set up signing. A fresh user must first create an EVM wallet and secure the seed phrase offline. Rain needs no caller API credential: the wallet signs and broadcasts locally, and Predictefy never sees its private key.
3. Fund it. Hold USDT on Arbitrum and a little ETH for gas. Start with at least 1 USDT for a limit buy; a sell must also meet 1 USDT of notional. Approve only the operator-armed per-market Diamond with a finite allowance. If your funds are on another chain, use GET /v1/bridge/quote as the assisted LI.FI route.
4. Allow time. Budget about 1–2 hours for a first wallet, bridge, and approval; an already-funded Arbitrum wallet is faster. The allowed sources list no Rain-specific geo gate, so confirm venue eligibility before funding.

What you need first

• Production status: Armed for build, submit, and cancel as verified on 2026-08-15. Hosted submit verifies the signed transaction and records signed; broadcasting remains client-owned.
• Wallet and chain: An EOA on Arbitrum (42161) signs and broadcasts the raw transaction.
• Venue account: The lane uses no account credential. Repository evidence does not establish whether Rain registration is required, so verify that prerequisite with the venue.
• Credentials: No caller venue credential enters the lane. The EOA private key and selected RPC remain in the caller’s process.
• Funding: Arbitrum USDT in the EOA, with a finite approval to the operator-armed per-market Diamond. The LI.FI helper can fund the wallet.

Production update — 2026-08-15

Rain’s earlier code-ready/default-off phase is superseded for production arming. The client-owned broadcast boundary and per-market safety checks below are unchanged.

Rain’s standard hosted order path is a source-verified LIMIT build. Omit action or set it to "limit"; choose orderSide: "BUY" or "SELL". The opt-in action: "market" path requires explicit slippage and deadline protection. action: "approve" remains available for the pool’s USDT allowance.

Every build resolves the pool Diamond from the Core catalog. Caller-supplied pool fields cannot replace it. At one pinned Arbitrum block, the server verifies that the pool’s FACTORY() is the official RainDeployer, its UUPS implementation, createdPools(pool), Arbitrum USDT with a 1e6 scale, and every required facetAddress(selector) route on that pool. A mismatch returns RAIN_POOL_SAFETY_CHECK_FAILED and no calldata.

Rain’s public option-side documentation is wrong

Verified V2 Solidity maps 1 = YES and 2 = NO; 0 reverts InvalidSide(). The API accepts YES/NO or 1/2 and rejects every other value. Option ids are 1-indexed, so option 0 is invalid.

For LIMIT builds:

Field	BUY	SELL
Quantity	amount: base-token atoms (Arbitrum USDT, 6dp)	shares: share atoms (6dp)
ABI	placeBuyOrder(option, side, price, amount, postOnly)	placeSellOrder(option, side, price, shares, postOnly)
Minimum	amount >= 1_000_000 (1 USDT)	shares * price / 1e18 >= 1_000_000
Phase	Order-book phase only	Order-book phase only

price is an integer string scaled by 1e18: 0.01e18 through 0.99e18, in exact 0.01e18 one-cent ticks. BUY’s fourth ABI argument is base-token amount; SELL’s same-position, same-type argument is shares. Swapping those units is rejected before calldata is built.

For protected market builds, provide slippageBps from 1 through 9999 and deadlineSecondsFromNow from 1 through 3600. Zero slippage is rejected because a zero minimum disables protection. The server reads the live block timestamp, uses getEntryShares for BUY or getSellProceeds for SELL, derives a nonzero minSharesOut/minAmountOut, and encodes an absolute Unix-seconds deadline. The duration itself is never encoded as the deadline. enterOption can execute in a live AMM phase or an order-book phase. Verified sellOption requires the order-book phase and is rejected during an AMM pool’s live window. The AMM-only getCurrentPrice, getImpactedPrice, and target-price-first getAmountRequired views are not used for order-book quotes.

Rain permits fewer than 50 active BUY orders and fewer than 50 active SELL orders per option/user. The source counters are per order direction, not keyed by YES/NO. A partial remainder below $0.10 does not rest: BUY dust is refunded and SELL dust remains available. These limits and the 1 USDT minimum surface as typed errors before signing.

Cancel one stored limit build through the standard cancel route and provide its emitted positive uint256 orderId. The server inherits option, side, price, owner, and BUY/SELL direction from the stored build and encodes cancelBuyOrders or cancelSellOrders as one scalar option plus three parallel one-element arrays. Cancel has no phase gate in the verified source.

Predictefy returns only unsigned {to,data,value}. The client signs and broadcasts on Arbitrum. Submit recovers the owner, pins chain 42161, byte-compares all three fields, and records signed; it never relays or claims a broadcast. The lane was introduced default-off and still requires RAIN_ENVIRONMENT, a read-only RAIN_RPC_URL, and explicit RAIN_MARKET_ADDRESSES; production’s 2026-08-15 arming supersedes only that earlier deployment state.