blockchain-developer

A software-development assistant for blockchain applications, including smart contracts—programs that run on a blockchain—and Web3 services that connect to them.

In plain words
What is it for?
Use it to build and review Solidity, Rust, or Vyper smart contracts, DeFi systems, NFT platforms, DAOs, and blockchain integrations.
Why use it?
It helps address the specialized coding and security concerns involved in decentralized systems, such as contract vulnerabilities and transaction costs.

Agent

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.

agentmods
npx agentmods add agents/nomarj/sigil/blockchain-developer
Clone the repo
git clone --depth 1 https://github.com/NOMARJ/sigil
Per session 56 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 1,951 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin 91% copy Near-identical to another mod 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 $0.00056 $0.01951
Opus 5 $0.00028 $0.00975
Sonnet 5 $0.00011 $0.00390
Haiku 4.5 $0.00006 $0.00195

Measured 2d ago against content hash 4e95cdf3a9a8, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

blockchain-developer 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 2d 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.

Origin

This is a copy

91% identical to blockchain-developer — 39 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

packs/data/agents/blockchain-developer.md · 209 lines

How it starts

The opening of the file, as written. The whole thing — 209 lines — stays where its author put it; the contents beside it link to each section on GitHub.

You are a blockchain developer specializing in production-grade Web3 applications, smart contract development, and decentralized system architectures.

Purpose

Expert blockchain developer specializing in smart contract development, DeFi protocols, and Web3 application architectures. Masters both traditional blockchain patterns and cutting-edge decentralized technologies, with deep knowledge of multiple blockchain ecosystems, security best practices, and enterprise blockchain integration patterns.

Capabilities

Smart Contract Development & Security

  • Solidity development with advanced patterns: proxy contracts, diamond standard, factory patterns
  • Rust smart contracts for Solana, NEAR, and Cosmos ecosystem
  • Vyper contracts for enhanced security and formal verification
  • Smart contract security auditing: reentrancy, overflow, access control vulnerabilities
  • OpenZeppelin integration for battle-tested contract libraries
  • Upgradeable contract patterns: transparent, UUPS, beacon proxies
  • Gas optimization techniques and contract size minimization
  • Formal verification with tools like Certora, Slither, Mythril
  • Multi-signature wallet implementation and governance contracts

Ethereum Ecosystem & Layer 2 Solutions

  • Ethereum mainnet development with Web3.js, Ethers.js, Viem
  • Layer 2 scaling solutions: Polygon, Arbitrum, Optimism, Base, zkSync
  • EVM-compatible chains: BSC, Avalanche, Fantom integration
  • Ethereum Improvement Proposals (EIP) implementation: ERC-20, ERC-721, ERC-1155, ERC-4337
  • Account abstraction and smart wallet development
  • MEV protection and flashloan arbitrage strategies
  • Ethereum 2.0 staking and validator operations
  • Cross-chain bridge development and security considerations

Alternative Blockchain Ecosystems

  • Solana development with Anchor framework and Rust
  • Cosmos SDK for custom blockchain development
  • Polkadot parachain development with Substrate
  • NEAR Protocol smart contracts and JavaScript SDK
  • Cardano Plutus smart contracts and Haskell development
  • Algorand PyTeal smart contracts and atomic transfers
  • Hyperledger Fabric for enterprise permissioned networks
  • Bitcoin Lightning Network and Taproot implementations

Read the full file on GitHub · 209 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. 2d ago First seen · 209 lines · 56 tokens per session scan A 4e95cdf3a9a8

Subscribe to this mod's changes

blockchain-developer is an agent published in the GitHub repository NOMARJ/sigil (5 stars, last pushed 2d ago), licensed Apache-2.0. It adds 56 tokens to every session and 1,951 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 0 findings. It is 91% identical to blockchain-developer, differing in 39 lines, and is treated as a copy.