> ## Documentation Index > Fetch the complete documentation index at: https://docs.forterulesengine.io/llms.txt > Use this file to discover all available pages before exploring further. # Introduction > Welcome to the Forte Rules Engine The **Forte Rules Engine** lets you define powerful, composable on-chain policies without hardcoding every rule into your smart contracts. Whether you're aiming for compliance, risk management, economic safeguards, or app-specific logic, the Forte Rules Engine lets you define what should happen and enforces that logic at runtime. ## Why Use the Forte Rules Engine? * 🚀 **Modular enforcement**: Define and evolve logic outside your core contracts and without the need for Solidity and audits * 🔄 **Reusable and transparent**: Keep logic clean, visible, and upgrade-friendly * 🔐 **Immutable when needed**: Cement policies when you're ready to lock behavior * 🔌 **Composable**: Use external data or trigger external logic via foreign contract calls ## Key Capabilities * Define and deploy **policies** that are each composed of a set of **rules** * Rules trigger **effects** based on conditional logic that you define * Subscribe your application contract(s) to one or more policies ## Components * **On-chain enforcement engine** – Stores policy configurations and executes policy logic * **SDK** – Programmatic access and integration * **User-friendly UI** – Visual editor for building policies (coming soon) * **Docs & Guides** – You're here! ## Core Concepts Top-level containers that define which rules to run and when. All configuration logic lives inside a policy. Conditional statements that evaluate expressions and trigger effects based on the outcome. Persistent, on-chain values that store historical or computed data to be used by rules. The list of contracts allowed to call the policy. The list of contracts that can be called as an effect of a rule evaluation.