// GLOSSARY -- BLOCKCHAIN & CRYPTO FUNDAMENTALS

What is Smart Contract?

1 min read Updated

A smart contract is a self-executing program stored on a blockchain that automatically enforces agreement terms when predefined conditions are met — eliminating the need for trusted intermediaries.

WHY IT MATTERS

Smart contracts are the building blocks of programmable finance. They're code at a blockchain address that can hold and transfer funds, enforce complex logic, interact with other contracts, and execute automatically — all tamper-proof.

The 'smart' is misleading — they're deterministic programs, not intelligent. They execute exactly as coded, which is both their strength (predictability) and weakness (bugs are permanent).

Smart contracts enable DeFi, NFTs, DAOs, and the entire Web3 application layer. Understanding them is fundamental to understanding crypto.

HOW POLICYLAYER USES THIS

PolicyLayer is itself a smart contract system. It uses on-chain contracts to enforce spending policies — limits, budgets, whitelists — that cannot be bypassed by AI agents. The same trustless enforcement that makes smart contracts powerful makes PolicyLayer's guardrails unbreakable.

FREQUENTLY ASKED QUESTIONS

What language are smart contracts written in?
Solidity (Ethereum/EVM) is dominant. Vyper is an alternative. Rust is used for Solana. Move for Aptos and Sui. Each reflects different design philosophies.
Can smart contracts be updated?
Not directly — deployed code is immutable. Upgradeable patterns exist (proxy contracts) that allow logic updates, but introduce trust assumptions about who can upgrade.
What happens if a smart contract has a bug?
On-chain code is immutable. Bugs allowing fund theft can mean permanent loss. This is why security audits, formal verification, and bug bounties are critical.

FURTHER READING

Enforce policies on every tool call

Intercept is the open-source MCP proxy that enforces YAML policies on AI agent tool calls. No code changes needed.

npx -y @policylayer/intercept
github.com/policylayer/intercept →
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