skill-creator

A guide for creating and improving reusable instructions for coding agents. It covers their structure, trigger wording, supporting files, and practical testing.

In plain words
What is it for?
Use it to create, refine, test, or troubleshoot an agent skill or its SKILL.md file.
Why use it?
It helps turn a repeated workflow into an instruction package that activates for the right requests and produces consistent results.

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/get-bb/bb/skill-creator
Any agent
npx skills add get-bb/bb --skill skill-creator
Clone the repo
git clone --depth 1 https://github.com/get-bb/bb

Made for: Claude Code, Codex.

Per session 54 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 924 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 $0.00054 $0.00924
Opus 5 $0.00027 $0.00462
Sonnet 5 $0.00011 $0.00185
Haiku 4.5 $0.00005 $0.00092

Measured 2d ago against content hash 0c8547ffa0ea, 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 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.

apps/server/src/services/skills/builtin-skills/skill-creator/SKILL.md · 122 lines

How it starts

The opening of the file, as written. The whole thing — 122 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Skill creator

Create skills that trigger for the correct requests and improve agent results.

Workflow

  1. Read the conversation and the existing skill before asking questions.
  2. Confirm the trigger, expected result, inputs, edge cases, and dependencies.
  3. Write or revise the skill and any required resources.
  4. Test realistic prompts in fresh BB threads.
  5. Compare the results with the previous skill or no-skill baseline.
  6. Revise until further changes do not give a useful improvement.

Ask only for decisions that the available context cannot answer. Match the amount of evaluation to the risk and the result quality that the user needs.

Skill contract

A skill uses this structure:

skill-name/
├── SKILL.md
├── references/
├── scripts/
└── assets/

Only SKILL.md is required. User skills live at ~/.bb/skills/<name>/SKILL.md.

The file starts with YAML frontmatter:

---
name: skill-name
description: State what the skill does and when an agent must use it.
---

The directory and name value must match. A name uses lowercase letters, numbers, and single hyphens. It cannot exceed 64 characters. The description cannot exceed 1024 characters.

Put all trigger conditions in the description. Include concrete tasks and nearby user phrases. Keep procedural instructions in the body.

BB discovers edits for newly spawned threads. An existing thread does not receive a skill revision after it starts.

Progressive disclosure

BB loads skill information in three levels:

  1. BB always loads the name and description.
  2. An agent reads SKILL.md after the skill triggers.
  3. The agent reads or runs bundled resources only when the task needs them.

Keep SKILL.md focused on routing, the main workflow, safety, and success criteria. Aim for fewer than 500 lines.

Move detailed variants, contracts, and examples into references/. Tell the agent exactly when to read each reference. Add a table of contents to reference files longer than 300 lines.

Read the full file on GitHub · 122 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 · 122 lines · 54 tokens per session scan A 0c8547ffa0ea

Subscribe to this mod's changes

skill-creator is a skill published in the GitHub repository get-bb/bb (2,888 stars, last pushed today), licensed MIT. It adds 54 tokens to every session and 924 once invoked, about $0.0003 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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