> For the complete documentation index, see [llms.txt](https://docs.t-rex.network/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.t-rex.network/reference/token-suite/utilitychecker.md). # UtilityChecker `UtilityChecker` is a read-only helper that tells, before a transfer is signed, whether it would pass and which check would refuse it. Every function takes the address of a token, so one deployment answers for every asset of a network. How to use it in an application is in [Pre-flight checks with UtilityChecker](/build/pre-flight-checks-with-utilitychecker.md). ### At a glance | | | | --------------- | ----------------------------------------------------------------------------------------------------------- | | **Source** | `contracts/utils/UtilityChecker.sol`, `contracts/utils/UtilityCheckerProxy.sol` | | **Interface** | `IUtilityChecker` | | **Deployed as** | One implementation behind a `UtilityCheckerProxy` (ERC-1967, UUPS), by `scripts/DeployUtilityChecker.s.sol` | | **Access** | Every function is a view open to anyone. `upgradeToAndCall` is reserved to the owner of the proxy | | **State** | Its owner and its implementation. Nothing about any token, and no role in any access manager | > **Trust statement.** `UtilityChecker` decides nothing: the token makes every check again when a transfer executes. Its owner can replace its code, so a wrong answer can mislead a display. It cannot move or block a token. ### Functions | Function | Returns | | ------------------------------------------------ | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | `getTransferStatus(_token, _from, _to, _amount)` | `_freezeStatus`: the token is not paused and `getFreezeStatus` reports no freeze. `_eligibilityStatus`: `TREXRegistry.isVerified(_to)`. `_complianceStatus`: every entry of `getTransferDetails` passes | | `getFreezeStatus(_token, _from, _to, _amount)` | `_frozen`: true when either address is frozen, or when the amount exceeds the available balance. `_availableBalance`: 0 when either address is frozen, the free balance of `_from` otherwise | | `getVerifiedDetails(_token, _userAddress)` | `_details`: one entry per required claim topic. `_walletStatus`: the status of the address in the `IdentityFactory`: `None`, `Active` or `Revoked` | | `getTransferDetails(_token, _from, _to, _value)` | `_details`: one entry per `RULE` module bound to the compliance of the token | ### The two structs | Struct | Field | Content | | ------------------------- | --------------- | -------------------------------------------------------------------------------------------------------------- | | `EligibilityCheckDetails` | `issuer` | The Claim Issuer whose claim was read for the topic. Zero when no trusted issuer made a claim | | | `topic` | The claim topic. 0 when no claim was found: take the topic from the list of required topics, at the same index | | | `pass` | The answer of `isClaimValid` on the issuer, or false when that call reverts | | `ComplianceCheckDetails` | `moduleName` | `IModule.name()` of the module | | | `allowedAmount` | `IModule.allowedAmount(ctx)` for this movement | | | `pass` | Whether the value is at most `allowedAmount` | ### Behaviors to know | Case | Behavior | | -------------------------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------- | | A transfer of zero | Not detected: the token reverts with `ZeroValue` | | `transferFrom` | The allowance and the spender policy are not read | | An address that resolves to no identity | `getVerifiedDetails` reverts as soon as one required topic has a trusted issuer. Read `TREXRegistry.identity(address)` first | | Several trusted issuers for one topic | `isVerified` accepts any valid claim. The entry of `getVerifiedDetails` describes the last issuer of the list | | A revoked wallet | The entries can all pass while `isVerified` is false: read `_walletStatus` | | Eligibility checks disabled on the registry | `_eligibilityStatus` is true for every address | | A sender with no identity while a `RULE` module is bound | `ModularCompliance.canTransfer` refuses. `getTransferDetails` still asks the modules and can report a pass | | Positions on satellites | Not read. The functions describe a movement on the reference chain | | A rule that is not monotonic | Its `allowedAmount` is the maximum or 0 for the amount asked, and says nothing about other amounts | The direct views give the decision without the detail: `Token.paused()`, `Token.isFrozen(address)`, `Token.freeBalanceOf(address)`, `TREXRegistry.isVerified(address)`, `ModularCompliance.canTransfer(from, to, amount)`. --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation by asking a question. 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