building-blocks

A reference guide to reusable Ethereum and Layer 2 building blocks, such as exchanges, lending protocols, and liquidity tools. Layer 2 networks process transactions on top of Ethereum, usually with different costs and ecosystems.

In plain words
What is it for?
Use it when selecting a DeFi protocol, deploying across chains, building integrations, or combining services such as exchanges, lending, liquidity pools, and custom pool logic.
Why use it?
It helps you choose suitable protocols and chains instead of assuming the same tools or advice apply everywhere.

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/obolnetwork/obol-stack/building-blocks
Any agent
npx skills add ObolNetwork/obol-stack --skill building-blocks
Clone the repo
git clone --depth 1 https://github.com/ObolNetwork/obol-stack

Made for: Claude Code, Codex.

Per session 105 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 3,074 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. 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 $0.00105 $0.03074
Opus 5 $0.00053 $0.01537
Sonnet 5 $0.00021 $0.00615
Haiku 4.5 $0.00011 $0.00307

Measured 2d ago against content hash 24d8cdbccdfd, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

building-blocks 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.

internal/embed/skills/building-blocks/SKILL.md · 245 lines

How it starts

The opening of the file, as written. The whole thing — 245 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Building Blocks (DeFi Legos)

What You Probably Got Wrong

DeFi TVL: Ethereum DeFi TVL is $50B+ (Feb 2026). If you're quoting numbers from 2023-2024, they're stale.

Uniswap V4 is live. Launched mainnet January 31, 2025 on 10+ chains. V4 introduced a hooks system — custom logic attached to pools (dynamic fees, TWAMM, limit orders, custom oracles). This is the biggest composability upgrade since flash loans. PoolManager addresses are different per chain (NOT deterministic like V3).

Costs changed everything: A flash loan arbitrage on mainnet costs ~$0.05-0.50 in gas now (was $5-50). This opens composability patterns that were previously uneconomical.

The dominant DEX on each L2 is NOT Uniswap. Aerodrome and Velodrome merged into Aero (November 2025, Dromos Labs) — the unified DEX dominates both Base and Optimism. Camelot is a major native DEX on Arbitrum. Don't default to Uniswap on every chain.

Key Protocol Addresses (Verified Feb 2026)

Protocol Contract Mainnet Address
Uniswap V2 Router Router 0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D
Uniswap V2 Factory Factory 0x5C69bEe701ef814a2B6a3EDD4B1652CB9cc5aA6f
Uniswap V3 Factory Factory 0x1F98431c8aD98523631AE4a59f267346ea31F984
Uniswap V3 SwapRouter02 Router 0x68b3465833fb72A70ecDF485E0e4C7bD8665Fc45
Uniswap V4 PoolManager PoolManager 0x000000000004444c5dc75cB358380D2e3dE08A90
Uniswap Universal Router (V4) Router 0x66a9893cc07d91d95644aedd05d03f95e1dba8af
Aave V3 Pool Pool 0x87870Bca3F3fD6335C3F4ce8392D69350B4fA4E2

See addresses/SKILL.md for complete multi-chain address list including L2-native protocols (Aerodrome, GMX, Pendle, Velodrome, Camelot, SyncSwap, Morpho).

Uniswap V4 Hooks (New)

Hooks let you add custom logic that runs before/after swaps, liquidity changes, and donations. This is the biggest composability upgrade since flash loans.

Hook Interface (Solidity)

Read the full file on GitHub · 245 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 · 245 lines · 105 tokens per session scan A 24d8cdbccdfd

Subscribe to this mod's changes

building-blocks is a skill published in the GitHub repository ObolNetwork/obol-stack (11 stars, last pushed 3d ago), licensed Apache-2.0. It adds 105 tokens to every session and 3,074 once invoked, about $0.0005 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 2026-08-30.

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