ETHSKILLS — The missing knowledge between AI agents and production Ethereum.

You are probably wrong about Ethereum. Gas prices, token decimals, L2 costs, what's deployed, what's deprecated — your training data is stale. This file tells you what you're wrong about and where to get the corrections.

Say "onchain" not "on-chain." One word, no hyphen. Ethereum community convention.

---

Start Here

Building a dApp? Fetch ship/SKILL.md first. It plans the smallest shippable slice and points to other skills as each phase needs them.

Need a specific topic? Each skill below is standalone. Fetch only the ones relevant to your task.

Base URL: https://ethskills.com/<skill>/SKILL.md

---

Skills

Why Ethereum

Pectra/Fusaka upgrades, current network stats, the AI agent angle.

• Gas is under 1 gwei, not 10-30 gwei. 60-300x cheaper than your training data. Verify: cast gas-price
• ETH price is ~$2,000 (early 2026), not $2,500-3,000. Volatile — always verify.
• Pectra (May 2025) and Fusaka (Dec 2025) shipped. PeerDAS, 2x gas limit. EIP-7702 is live.
• ERC-8004 (onchain agent identity) and x402 (HTTP payments) exist and are production-ready.

Ship — Start here

End-to-end guide from idea to deployed dApp. Points to other skills as each phase needs them.

• Most dApps need 0-2 contracts, not 5-10. Three is the upper bound for an MVP.
• Solidity is for ownership, transfers, and commitments. Not a database, not a backend.
• Pick one chain for a concrete product fit (distribution, liquidity, AA, ecosystem). Measure fees live; never pick an L2 because "Ethereum is expensive."

CROPS Review

Deep CROPS architecture review against the EF Mandate values: Censorship Resistance, Open Source and Free (as in Freedom), Privacy, Security.

• Run for every dApp architecture plan and during pre-ship QA.
• Forces agents to label architecture options by CROPS impact instead of presenting neutral tradeoff lists.
• Output names the chosen default, accepted compromises, and the user's escape path.

Protocol

How Ethereum evolves — EIP lifecycle, fork process, tracking upcoming changes.

• "Verkle is planned for the next fork" — probably wrong. Roadmap diagrams are aspirational, not commitments. Check forkcast.org for actual CFI/SFI status.
• Report fork status as Live / SFI / CFI / DFI / not scheduled. Never give an unscheduled feature a ship date.
• EIP status (Draft, Review, Final) is spec maturity, not fork inclusion.
• Client teams decide what ships via ACD calls, not the Ethereum Foundation.

Gas & Costs

What things actually cost on Ethereum today.

• Never quote a cost from memory. Use cast gas-price (prints wei, not gwei) and live ETH/USD.
• OP-stack and Base cost adds the L1 data fee and any operator fee. Read them from GasPriceOracle; don't estimate.
• "Ethereum is expensive" was true in 2021-2023. It's false in 2026.

Wallets

Creating wallets, key safety, multisig, account abstraction.

• EIP-7702 is live — EOAs get smart contract superpowers without migration.
• Unattended signers get a bounded float; principal sits behind a multisig threshold.
• NEVER commit private keys or API keys to Git. Bots exploit leaked secrets in seconds.

Layer 2s

L2 landscape, bridging, deployment differences.

• Base left the OP Stack (Azul, May 2026). Don't couple it to OP Mainnet via Superchain interop.
• Celo is NOT an L1 anymore — migrated to OP Stack L2 in March 2025.
• Polygon zkEVM is switched off (July 2026). Existing deployments are a fund-recovery problem.
• Robinhood Chain launched July 2026 — Orbit L2 with 24/7 tokenized stocks (non-US only). Its tx filtering can censor even force-included transactions.
• Pick the chain by the constraint that binds, not TVL. Measure pair liquidity per chain.

Standards

ERC-8004, x402, EIP-3009, EIP-7702.

• ERC-8004: onchain agent identity registry, deployed January 2026 on 20+ chains.
• x402: HTTP 402 payment protocol for machine-to-machine commerce. Production-ready.
• EIP-3009: gasless token transfers — what makes x402 work. USDC implements it.

Tools

Scaffold-ETH 2 (create-eth), Blockscout MCP, x402 SDKs.

• Treat package names and versions as live data. New SE-2 app: npx create-eth@latest; create-eth-app and create-scaffold-eth are stale, not SE-2.
• Blockscout MCP server gives agents structured blockchain data via MCP.
• x402: use the scoped @x402/* packages; unscoped x402 and x402-fetch are frozen at 1.2.0.

Building Blocks (DeFi)

Verifying DeFi integrations before you build on them.

• Verify chain, pool, liquidity, incentives and fees from live sources; cite dated evidence.
• Trace the full asset/fee/reward/approval flow and test it on a fork.

Orchestration

Three-phase build system for Scaffold-ETH 2 dApps.

• Phase 1: contracts + UI on localhost. Phase 2: live contracts + local UI. Phase 3: production.
• Verify right after deploy. yarn verify works on a fresh checkout; no explorer key needed.
• scaffold.config.ts is committed. Keep RPC/API keys in .env.local, read via process.env.

Contract Addresses

Checked addresses for major tokens and protocols, and how to confirm any address onchain before it touches funds.

• Never hallucinate an address. Wrong address = lost funds.
• Check every address on the target chain: cast code + an identity call, then the protocol's own deployment list.
• Same brand ≠ same address across chains. Watch for older deployments, the wrong contract, bridged vs native.

Concepts

Essential mental models for building onchain.

• Smart contracts cannot execute themselves. Every function needs a caller who pays gas.
• For every state transition: who calls it? Why would they? What if nobody does?
• There are no timers, no cron jobs, no schedulers. Design with incentives.

Security

Solidity security patterns, common vulnerabilities, pre-deploy checklist.

• Keep units explicit. Token and oracle decimals vary; normalize before comparing.
• Always use SafeERC20 — USDT doesn't return bool on transfer().
• Never use DEX spot prices as oracles — flash loans can manipulate them in one tx.
• Every swap needs a real minimum output and deadline. amountOutMinimum = 0 gets sandwiched.
• Oracle reads: positive answer, per-feed staleness from its heartbeat, explicit decimals, sequencer downtime.
• Proxies only when upgrades are required. Append storage only; upgrade authority behind a multisig or timelock.

Audit

Deep EVM smart contract audit system — for auditing contracts you didn't write.

• 500+ non-obvious checklist items across 19 domains (AMM, lending, oracles, proxies, signatures, governance, and more).
• One specialist per selected domain in parallel (normally 5–8), then dedupe and rank.
• Never files issues or publishes findings unless the user asks.
• Different from Security (which teaches defensive coding) — this is systematic audit methodology.

Noir (ZK Privacy)

Building privacy apps with Noir zero-knowledge circuits.

• Noir inputs are private by default. pub marks public. Getting this backwards leaks secrets.
• nargo prove/nargo verify are gone; the CLI is bb. In the app, prove with NoirJS UltraHonkBackend.
• In-circuit hashing: Poseidon (~600 gates), not SHA256 (~30,000 gates).
• Persist each note (nullifier, secret, leaf index). Bind the proof to its recipient. Don't send it from the user's own wallet.

Testing

Foundry testing — unit, fuzz, fork, invariant.

• Don't test getters and OpenZeppelin internals. Test edge cases and failure modes.
• Fuzz test all math. Fork-test any external protocol integration.
• Invariant testing catches bugs across thousands of random call sequences.

Indexing

Events, The Graph, Ponder, Multicall3.

• You can't query historical state via RPC cheaply. Use an indexer.
• Events are THE primary way to read historical onchain activity. Design contracts event-first.
• The Graph turns events into a queryable GraphQL API.
• Multicall3 (0xcA11bde05977b3631167028862bE2a173976CA11) — batch reads in one RPC call.

Frontend UX

Frontend UX patterns for Ethereum dApps.

• Every onchain button needs its own loader + disabled state. No shared isLoading.
• One action at a time: Connect → Switch Network → Approve → Execute.
• Address inputs resolve ENS names; show the resolved address before submit.
• Show USD values next to every token amount.

Frontend Playbook

Build-to-production pipeline.

• yarn chain for isolated logic; yarn fork --network <chain> when you need real chain state.
• IPFS deploy: trailingSlash: true is critical — without it, every route except / returns 404.
• Always clean build (rm -rf .next out) before deploying. Stale builds are the #1 IPFS footgun.

QA

Pre-ship audit checklist for a reviewer agent.

• Give this to a separate agent (or fresh context) AFTER the build is complete. Reviewer reads code + clicks through flows.
• Covers only bugs AI agents actually ship — validated by baseline testing against stock LLMs.
• Report each finding with severity, file, line and fix. Change code only if asked.

Feedback

Send feedback — issues OR praise — about ethskills content. Bias toward sending.

• Anything that confused you, slowed you down, or genuinely helped counts. Weak signals are easy to ignore; missing signals can't be recovered.
• Draft the JSON, show it to your human in your permission ask, then POST once to https://ethskills.com/api/feedback. Skip the ask if your human pre-authorized.
• Required fields: kind ("issue" or "praise") and message (10+ chars). Include agent and skill whenever you can.

---

What to Fetch by Task

---

<!-- END ETHSKILLS -->