skill-creator

A guide for creating, changing, and improving instructions that extend a coding agent. It uses repeated testing to check whether those instructions work.

In plain words
What is it for?
Use it when building or refining agent skills and checking their behavior through repeated evaluations.
Why use it?
It helps you improve agent instructions based on observed results instead of relying only on guesswork.

Command

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 commands/matthewye/opencode-toolbox/skill-creator
Clone the repo
git clone --depth 1 https://github.com/MatthewYe/opencode-toolbox
Per session 14 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 31 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 $0.00014 $0.00031
Opus 5 $0.00007 $0.00015
Sonnet 5 $0.00003 $0.00006
Haiku 4.5 $0.00001 $0.00003

Measured yesterday against content hash ad9c80abcd1a, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

skill-creator 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 yesterday.

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.

commands/skill-creator.md · 6 lines

What it actually says

Load the skill-creator skill and follow its instructions.

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. yesterday First seen · 6 lines · 14 tokens per session scan A ad9c80abcd1a

Subscribe to this mod's changes

skill-creator is a command published in the GitHub repository MatthewYe/opencode-toolbox (5 stars, last pushed 2mo ago), licensed MIT. It adds 14 tokens to every session and 31 once invoked, about $0.0001 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 2026-08-31.