> ## Documentation Index
> Fetch the complete documentation index at: https://docs.cow.bleu.builders/llms.txt
> Use this file to discover all available pages before exploring further.

# ISwapGuard

> API reference for the ISwapGuard interface that enables order settlement restrictions in ComposableCoW.

# ISwapGuard

The `ISwapGuard` interface enables CoW Protocol to restrict order settlements through ComposableCoW by implementing a verification mechanism.

## Core Function

The interface requires a single `verify()` function that evaluates whether an order meets security criteria before settlement. This function receives:

| Parameter       | Type                     | Description                                                                             |
| --------------- | ------------------------ | --------------------------------------------------------------------------------------- |
| `order`         | `GPv2Order.Data`         | The CoW Protocol order data                                                             |
| `ctx`           | `bytes32`                | Context identifier (either `bytes32(0)` for merkle trees or a hash for cabinet lookups) |
| `params`        | `ConditionalOrderParams` | Programmatic order parameters                                                           |
| `offchainInput` | `bytes`                  | Optional off-chain verification input                                                   |

The function returns a boolean indicating approval.

## Implementation Examples

### ReceiverLock

Restricts orders to self-transfers only, preventing fund redirection by ensuring the receiver is set to `address(0)`.

### TokenWhitelistGuard

Maintains an approved token list, validating both the sell and buy tokens against this whitelist.

### AmountLimitGuard

Enforces maximum trade sizes by checking the sell amount against a configured limit.

## Key Requirements

* Implementations should inherit from `BaseSwapGuard` for proper ERC-165 interface support
* Verification logic must remain stateless, deterministic, and gas-efficient since it executes during order validation

<Warning>
  Guards represent security-critical components requiring thorough testing before production deployment. Guards cannot prevent malicious order handlers from being used.
</Warning>