fix stale branding and incorrect event name in NatSpec

- "order book interface" → "Raindex interface" in import comment
- `AddOrder` → `AddOrderV3` to match actual event name
- Add Raindex description and comparisons to README
- Remove dangling ZeroExOrderBookFlashBorrower reference

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: thedavidmeister

README.md

@@ -1,3 +1,47 @@
+## Raindex
+
+Raindex is a programmable, dynamic onchain order book. Orders are not static
+limit orders — they are strategies written as Rain interpreter expressions that
+evaluate at match time. This means order amounts and ratios can change based on
+onchain state, time, oracle prices, or any other logic the expression author
+encodes. Two orders clear when their evaluated ratios overlap, with any surplus
+going to the clearer as a bounty.
+
+### Raindex vs. traditional order books
+
+Traditional onchain order books (e.g. dYdX, Serum) replicate the familiar
+limit-order model: users place fixed-price bids and asks, a matching engine
+pairs them, and fills execute at the stated price. This works, but each
+repricing requires a new transaction, making active market-making expensive
+and slow.
+
+Raindex replaces static prices with executable expressions. An order's ratio
+and maximum amount are computed fresh every time someone attempts to match it.
+The expression can read any onchain state — block number, oracle feeds, vault
+balances, its own persistent storage — so a single order can implement
+strategies that would otherwise require off-chain bots continuously cancelling
+and reposting.
+
+### Raindex vs. AMMs
+
+AMMs (Uniswap, Curve, Balancer) achieve always-on liquidity by pooling tokens
+into a shared reserve governed by a bonding curve. Liquidity providers deposit
+tokens and receive pool shares; the curve mechanically sets the price. This
+removes the need for active order management but introduces impermanent loss,
+pool-level MEV extraction, and limited strategic control for individual LPs.
+
+Raindex keeps individual ownership of tokens in per-user vaults — there is no
+shared pool. Each order owner defines their own pricing logic, so there is no
+bonding curve imposing a single price on all participants. Because orders
+evaluate independently, one user's strategy cannot dilute or override another's.
+Clearers (analogous to AMM arbitrageurs) match overlapping orders and keep the
+surplus, providing the same "always available" clearing incentive that
+arbitrageurs provide to AMMs, but without requiring passive LPs to share a
+pool.
+
+This repo defines the Solidity interfaces and types for Raindex. It does not
+contain the implementation.
+
 ## Dev stuff
 
 ### Local environment & CI

src/interface/IRaindexV6.sol

@@ -14,7 +14,7 @@ import {
     IInterpreterStoreV3
 } from "../../lib/rain.interpreter.interface/src/interface/IInterpreterCallerV4.sol";
 
-/// Import unmodified structures from older versions of the order book interface.
+/// Import unmodified structures from older versions of the Raindex interface.
 import {
     ClearStateChangeV2,
     ClearConfigV2,
@@ -115,8 +115,7 @@ struct TakeOrdersConfigV5 {
 /// against Raindex expressions. All deposited tokens across all vaults are
 /// available for flashloan, the flashloan MAY BE REPAID BY CALLING TAKE ORDER
 /// such that Raindex's liability to its vaults is decreased by an incoming
-/// trade from the flashloan borrower. See `ZeroExOrderBookFlashBorrower` for
-/// an example of how this works in practise.
+/// trade from the flashloan borrower.
 ///
 /// Token amounts and ratios returned by calculate order MUST be rain floating
 /// point values. Handle IO will receive these values as floating point values.
@@ -432,7 +431,7 @@ interface IRaindexV6 is IERC3156FlashLender, IInterpreterCallerV4 {
     ///
     /// If the order already exists, the Raindex MUST NOT change state, which
     /// includes not emitting an event. Instead it MUST return false. If the
-    /// Raindex modifies state it MUST emit an `AddOrder` event and return
+    /// Raindex modifies state it MUST emit an `AddOrderV3` event and return
     /// true.
     ///
     /// If vault ID is `0` for any input or output, this indicates a vaultless