A rule is the core decision-making unit within a policy. Each rule defines a condition expression that is evaluated during a contract call—and one or more effects that are triggered based on whether that condition expression evaluates to true or false.

Rules are executed in the order they appear in the policy. This matters when one rule affects data (like a tracker) used by another.

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Anatomy of a Rule

Every rule consists of:

  • ✅ Name
  • 📝 Description
  • 🔍 Condition expression
    An expression that must evaluate to a boolean (true or false)
  • 🎯 Effects when true
    What happens if the condition expression evaluates to true
  • 🚫 Effects when false
    What happens if the condition expression evaluates to false
  • 🔢 Execution order
    Rules run sequentially—this order is defined in the policy configuration

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Condition Expressions

Condition expressions are defined by a sequence of values, operators, and optional parentheses. These expressions evaluate to true or false and control whether the “true” or “false” effects run.

Supported operators include:

TypeOperators
Arithmetic+, -, *, /
Comparators>, <, >=, <=, ==, !=
LogicalAND, OR, NOT

Values in an expression can come from:

  • Config data — set at configuration time
  • Available data - sent from the calling contract, e.g. sender, token ID, method, timestamp, balance
  • Trackers — on-chain values managed by your policy
  • Foreign calls — values returned by external smart contract calls

🧠 Expressions follow standard operator precedence rules and can use parentheses for grouping.

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Effects

Each rule must define at least one effect that takes place if the condition expression evaluates to true or false. You can include multiple effects in either branch. These can be:

  • revert: cancel the transaction
  • emit event: emit an ethereum event
  • update tracker: update a tracker’s value
  • call external contract: call a foreign contract

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Example Rule (pseudo format)

name: "Limit daily transfer amount"
description: "Cap the amount a user can send per day to 100"
condition: tracker.dailyTransferred(sender) + transaction.amount <= 100
onTrue:
  - updateTracker: dailyTransferred(sender) += transaction.amount
onFalse:
  - revert: "Transfer exceeds daily limit of 100"