What is extract-function?

A refactoring guide for moving a block of code into a named function with suitable types and tests.

Extract a selected code block, choose a descriptive function name, add the replacement call, include documentation where appropriate, and identify possible reuse.

It helps reduce tangled code by identifying the block’s inputs, outputs, and single responsibility before changing it.

extract-function — Skill by berkcangumusisik

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/berkcangumusisik/claude-code-practices/extract-function

Any agent

npx skills add berkcangumusisik/claude-code-practices --skill extract-function

Clone the repo

git clone --depth 1 https://github.com/berkcangumusisik/claude-code-practices

Made for: Claude Code, Codex.

Per session 17 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 237 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.

Model	Per session	Once invoked
Fable 5	$0.00017	$0.00237
Opus 5	$0.00009	$0.00118
Sonnet 5	$0.00003	$0.00047
Haiku 4.5	$0.00002	$0.00024

Measured 3d ago against content hash f719b5e13fbb, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

extract-function 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 3d 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/extract-function/SKILL.md · 34 lines

What it actually says