blockchain-web3

blockchain-web3 is a skill for Claude Code, Codex from j4flmao/agent-skills. It costs 128 tokens per session (5,204 once invoked), scanned A, original, MIT.

A guide to building web3 applications—apps that connect to blockchains—using wallet connections, blockchain libraries, and transaction flows.

In plain words
What is it for?
Use it to plan TypeScript frontends with ethers.js, viem, or wagmi, including wallet integration, reading and writing contract data, events, signing, and account abstraction.
Why use it?
It helps handle the differences between ordinary web requests and blockchain actions that require wallets, signatures, network calls, and transaction confirmation.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one.

Good fit Use it to plan TypeScript frontends with ethers.js, viem, or wagmi, including wallet integration, reading and writing contract data, events, signing, and account abstraction.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/j4flmao/agent-skills/blockchain-web3
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent
npx skills add j4flmao/agent-skills --skill blockchain-web3
Clone the repo
git clone --depth 1 https://github.com/j4flmao/agent-skills

Made for: Claude Code, Codex.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for blockchain-web3

README.md
[![agentmods](https://agentmods.dev/badge/skills/j4flmao/agent-skills/blockchain-web3/github.svg)](https://agentmods.dev/skills/j4flmao/agent-skills/blockchain-web3)
Your own site
<a href="https://agentmods.dev/skills/j4flmao/agent-skills/blockchain-web3"><img src="https://agentmods.dev/badge/skills/j4flmao/agent-skills/blockchain-web3/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for blockchain-web3

Your own site · 80×15
<a href="https://agentmods.dev/skills/j4flmao/agent-skills/blockchain-web3"><img src="https://agentmods.dev/badge/skills/j4flmao/agent-skills/blockchain-web3.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 128 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 5,204 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe. Third-party audits
  • NVIDIA SkillSpector warn 7 Sept 2026
SkillSpector: 1 finding, up to medium

These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →

  • medium Excessive Agency · line 395
    Skill enables autonomous high-impact decisions without human-in-the-loop verification. Critical operations (destructive commands, financial transactions, data deletion) should require explicit user confirmation.
    Fix: Add human-in-the-loop confirmation for destructive, irreversible, or high-impact operations. Never auto-execute commands that modify files, send data, or alter system state.
How audits are shown
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00128 $0.05204
Opus 5 $0.00064 $0.02602
Sonnet 5 $0.00026 $0.01041
Haiku 4.5 $0.00013 $0.00520

Measured 5d ago against content hash 7568c4e232d0, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-09, from the pricing page.

Security

Grade A, and why

blockchain-web3 scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 5d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

skills/blockchain/blockchain-web3/SKILL.md · 597 lines

How it starts

The opening of the file, as written. The whole thing — 597 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Blockchain Web3

Purpose

Guide web3 frontend and dApp development covering library selection, wallet integration, contract interaction, transaction management, event handling, and account abstraction. Focuses on TypeScript-based frontend patterns.

Agent Protocol

Trigger

"web3", "ethers.js", "viem", "wagmi", "web3.js", "metamask", "phantom wallet", "walletconnect", "dapp", "decentralized app", "react blockchain", "nextjs web3", "ethers contract", "contract interaction", "read contract", "write contract", "send transaction", "sign message", "eip-1193", "eip-4337", "account abstraction", "multicall", "rpc provider", "infura", "alchemy", "blockchain frontend", "typechain", "wagmi hooks", "viem client", "user operation", "sign typed data"

Input Context

  • Frontend framework (React/Next.js/Vanilla)
  • Blockchain networks (Ethereum/L2/Solana/Multi-chain)
  • Library preference (viem+wagmi/ethers.js/web3.js)
  • Features needed (read/write/events/wallet/signing)
  • Account abstraction requirements (ERC-4337)
  • Performance requirements (RPC calls, caching, multicall)

Output Artifact

Web3 frontend architecture: library selection, provider setup, wallet connection flow, contract interaction patterns, event handling, and transaction management.

Response Format

  1. Library selection: viem/wagmi vs ethers.js vs web3.js rationale
  2. Provider setup: chain config, RPC endpoints, fallback providers
  3. Wallet connection: injected providers (EIP-6963), WalletConnect, smart accounts (ERC-4337)
  4. Contract interaction: read/write patterns, event listening, multicall
  5. Transaction flow: gas estimation, simulation, submission, confirmation tracking
  6. Error handling: revert reasons, user rejection, network errors, rate limiting

Completion Criteria

  • Library selection justified with comparison against alternatives
  • Provider setup handles: multiple chains, fallback RPCs, rate limiting
  • Wallet connection supports: EIP-1193, EIP-6963, WalletConnect
  • Transaction management handles: gas estimation, simulation, confirmation, error states
  • Event handling covers: subscription, polling, historical query, reorg handling

Read the full file on GitHub · 597 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 5d ago First seen · 597 lines · 128 tokens per session scan A 7568c4e232d0

Subscribe to this mod's changes

blockchain-web3 is a skill published in the GitHub repository j4flmao/agent-skills (22 stars, last pushed 2d ago), licensed MIT. It adds 128 tokens to every session and 5,204 once invoked, about $0.0006 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.

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