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Onchain reads, decoded.

Guides, comparisons, integrations, reference docs, and trust reports for reading smart contract data from Claude, your code, n8n, or a REST client.

A 13-part series

Ethereum, explained

Short tutorials on how Ethereum works, from smart contracts to price oracles. Each part reads a real contract live.

Start with part 1
  1. 1What is a smart contract?
  2. 2What is the EVM (Ethereum Virtual Machine)?
  3. 3EIP vs ERC: Ethereum standards explained
  4. 4What is ERC-20? Tokens and approvals
  5. 5What is wrapped bitcoin? WETH and WBTC explained
  6. 6ERC-721 vs ERC-1155: NFT standards explained
  7. 7What is gwei? Gas fees and EIP-1559
  8. 8What is ENS? Ethereum Name Service explained
  9. 9What is a multisig wallet? M-of-N and Safe
  10. 10What is account abstraction?
  11. 11What is EIP-712? Permits and signing
  12. 12What is an upgradeable proxy contract?
  13. 13What is a blockchain oracle? Price feeds explained
Etherscan API on Base and BNB Chain: reading contract data without a paid API key
Guide

Etherscan API on Base and BNB Chain: Reading Contracts Without a Paid Key

Etherscan's free API key no longer covers Base or BNB Chain. Here is what still works, how to read contracts there without a paid plan, and when to pay for history.

evmquery Monitors: an expression checked on a schedule that notifies a webhook
Guide

Introducing evmquery Monitors: Onchain Alerts Without the Cron Script

evmquery Monitors check an expression against live chain state on a schedule and notify you by email or webhook. Free plan included, no cron job to run.

Two trigger types for an evmquery monitor: a condition edge and a change from a baseline
Guide

Smart Contract Alert Conditions: Condition vs Change Triggers for evmquery Monitors

Write a smart contract alert condition that fires when you want it. Condition and change triggers for evmquery monitors, with six real expressions.

Claude calling the evmquery create_monitor tool to watch a USDC balance
Guide

Monitor a Smart Contract from Claude or Cursor with the evmquery MCP Server

Create, pause and inspect smart contract monitors from Claude or Cursor with seven evmquery MCP tools. Example prompts, tool calls and reading events back.

A TypeScript webhook receiver forwarding an evmquery monitor event to a chat channel
Guide

Smart Contract Webhook: Receive evmquery Monitor Alerts in TypeScript

Build a smart contract webhook receiver for evmquery monitors: payload shape, deduping on event id, digests, retries and forwarding to chat.

A single key beside a smart account that adds a rulebook of limits, recovery, batching and sponsored gas
Reference

What is account abstraction?

Account abstraction turns a wallet into a smart account whose rules are code. ERC-4337 creates a new smart account, and EIP-7702 upgrades an existing address.

A blockchain on the left and the outside world on the right, joined by an oracle that carries a price across
Reference

What is a blockchain oracle? Price feeds explained

A blockchain oracle publishes outside data, such as a price, onto the chain for smart contracts to read. A price feed holds the latest price of one asset pair.

ERC-721 as numbered concert seats next to ERC-1155 as a shop shelf with stock counts
Reference

ERC-721 vs ERC-1155: NFT standards explained

ERC-721 gives every NFT token ID exactly one owner. ERC-1155 holds many token types in one contract and tracks how many of each type every address holds.

A paper proposal moving through stages toward a stamped Ethereum standard
Reference

EIP vs ERC: Ethereum standards explained

An EIP is a public proposal for a change or convention on Ethereum. An ERC is an EIP in the application category, such as the ERC-20 token standard for tokens.