web3-dev

A coding guide for building apps and tools that read blockchain data through the Blockscout PRO API, an HTTP service covering more than 100 EVM-compatible blockchain networks.

In plain words
What is it for?
Use it to build decentralised apps, wallets, bots, analytics tools, command-line programs, or other software that reads blockchain data and contract state.
Why use it?
It avoids connecting separately to each blockchain network and provides structured explorer data such as transactions, tokens, NFTs, and contract information.

Skill for Claude CodeCodex

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

Made for: Claude Code, Codex.

Per session 212 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 7,142 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 1 finding. Scan, not verified.
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 $0.00212 $0.07142
Opus 5 $0.00106 $0.03571
Sonnet 5 $0.00042 $0.01428
Haiku 4.5 $0.00021 $0.00714

Measured 2d ago against content hash c3b62963091b, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

web3-dev scanned grade A with 1 finding 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.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

curl --request GET \
web3-dev/SKILL.md · 350 lines

How it starts

The opening of the file, as written. The whole thing — 350 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Web3 Dev — Blockscout PRO API

This skill teaches the agent how to build software (apps, scripts, CLIs, bots, mobile/desktop clients) that reads blockchain data through the Blockscout PRO API — a single HTTP API covering 100+ EVM chains (94+ L2s and scaling projects). One API key works on every supported chain; switch chains by changing the chain_id path parameter on the call.

The PRO API returns explorer-enriched data: indexed, decoded, and structured — token metadata, proxy implementations, internal transactions, contract context, and so on. Use it for dApps and wallets, AI agents and bots, analytics platforms, and operational tooling.

For data the explorer has not pre-indexed — most importantly live or historical contract state at a specific block (e.g. balanceOf(addr) against a token contract at block N, totalSupply() at a past block, any view-function call, contract storage reads) — the PRO API also exposes eth_call through its JSON-RPC gateway. See Reading contract state. The same Bearer-token auth covers both surfaces; you do not need a separate RPC endpoint for historical contract reads.

The bundled files in references/ are the single source of truth for which endpoints exist and how to call them:

File Purpose
references/pro-api-index.md One-line summary of every endpoint, grouped by OpenAPI tag. Always start here.
references/pro-api.json Full OpenAPI v3 specification (~24,000 lines). Do not read whole — query it with oastools.

Do not classify endpoints into your own "families" or steer the user toward a subset. Every endpoint listed in the index is callable, and every endpoint uses the same authentication scheme described below.

API key — mandatory pre-flight

A PRO API key is required for every PRO API call. Run the following pre-flight before issuing the first request in a session.

Pre-flight check (in this order)

Read the full file on GitHub · 350 lines

Files

What ships with it

4 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

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 · 350 lines · 212 tokens per session scan A c3b62963091b

Subscribe to this mod's changes

web3-dev is a skill published in the GitHub repository blockscout/agent-skills (30 stars, last pushed 2mo ago), licensed MIT. It adds 212 tokens to every session and 7,142 once invoked, about $0.0011 per session on Opus 5. A static security scan graded it A with 1 finding (makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.