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.
npx agentmods add rules/ccashwell/evm-cortex/skill-developmentgit clone --depth 1 https://github.com/ccashwell/evm-cortexWhat 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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5 | $0.00316 | $0.00316 |
| Opus 5 | $0.00158 | $0.00158 |
| Sonnet 5 | $0.00063 | $0.00063 |
| Haiku 4.5 | $0.00032 | $0.00032 |
Grade A, and why
skill-development 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.
What it actually says
Skill Development Rules
Skill Directory Structure
Each skill lives in its own directory under skills/:
skills/
gas-optimization/
SKILL.md # Skill metadata + content
SKILL.md Format
---
name: skill-name
description: When and why to use this skill. Used for auto-discovery.
---
Followed by the skill content in Markdown.
Naming Conventions
- Directory name:
kebab-case(e.g.,gas-optimization) - SKILL.md name field: same as directory name
- Description: explains WHEN to trigger in Ethereum context
Quality Rules
- Content must be Ethereum/Solidity specific
- Include Solidity code examples where applicable
- Include checklists for complex patterns
- Reference specific EIPs, ERCs, and tools
- Cross-reference related skills
- Use "onchain" not "on-chain"
Skill Categories
- Solidity Development: patterns, gas, storage, assembly
- Security: vulnerability patterns, attack vectors, defenses
- DeFi: protocol integration, AMMs, lending, oracles
- Testing: Foundry testing, fuzzing, invariants, formal verification
- Audit: pipeline phases (prep, recon, breadth, depth, verify, report)
- Standards: ERC implementations, proxy patterns
- Tooling: Foundry, Slither, Cast, Anvil
- Infrastructure: subgraphs, frontends, L2, deployment
Consider these rules if they affect your 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.
- 2d ago First seen · 48 lines · 316 tokens per session scan A 5b50ccba7f98
skill-development is a cursor rule published in the GitHub repository ccashwell/evm-cortex (127 stars, last pushed 22d ago), licensed MIT. It adds 316 tokens to every session, about $0.0016 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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