Create new bb skills and improve existing ones. Use this whenever the user wants to make, write, author, draft, edit, refine, or optimize a skill — including turning the current conversation or workflow into a reusable skill, fixing a skill that is not triggering, or sharpening a skill's description. Skills live in ~/.bb/skills/<name>/SKILL.md.
SkillScore77Maintained
Automatic
◆AI Engineer pack
Last verified 9/9/2026
What it changes
Passed 14 of 18 test cases with the skill, and 11 of 18 without it.
Without skill59%
With skill77%
Checks it passed that the model alone missed
Output templates are placed in an assets subfolder
The file path is specified as ~/.bb/skills/code-review/SKILL.md
Advises omitting generic advice and model-specific scaffolding from the skill entrypoint
and 2 more in the full report
5 fixed12 passed either way4 still failing1 broke
Pass-rate lift
+18 pp
Tokens
-29%
Agent turns
0%
Response time
-38%
Model gemini-3.6-flashMeasured 9/9/2026v317 of 22 cases passed with skill · 18 comparable
Tokens, turns and time describe resource use, not a dollar price.
See it in action
One of 5 test cases the skill fixed. Same model, same prompt, with and without the skill.
1 of 5
Prompt
I want to name a new BB user skill `Docker_Container_Helper_v2.0!` in my entrypoint frontmatter. Generate the header block using this name.
What was checked, without and with the skill
Checked
Without skill
With skill
The skill name is sanitized to lowercase letters, numbers, and single hyphens such as docker-container-helper-v2
Missed
Passed
case-08 · gemini-3.6-flash · 9/9/2026 · answers are capped and redacted
What's inside
The instructions your model reads when the skill loads.
SKILL.md57 lines2 files
Skill creator
Create skills that add useful domain knowledge and trigger only for relevant tasks.
User skills live at ~/.bb/skills/<name>/SKILL.md. Edit built-in and plugin
skills at their source, not in generated runtime copies.
Contract
Start SKILL.md with YAML frontmatter:
---
name: skill-name
description: Briefly state the capability and when it applies.
---
The directory and name must match. Names use lowercase letters, numbers, and
single hyphens, with at most 64 characters. Descriptions have a 1024-character
limit; use a short, discriminating sentence rather than filling that limit.
Preserve supported metadata and invocation settings when editing.
BB loads names and descriptions for discovery, the body when a skill is used,
and supporting files when needed. New threads discover revisions; existing
threads may retain the version they started with.
Write for the task
Keep the purpose, essential constraints, completion criteria, and reference
routing in the entrypoint. A short skill needs no extra files.
Move substantial mode-specific procedures and examples into references/.
State when to read each file; do not require loading every reference.
Use scripts/ for repeated deterministic work and assets/ for output
templates or resources. Reuse existing resources before adding new ones.
Describe outcomes and decision boundaries. Reserve rigid steps for fragile
operations where order matters; avoid generic advice, repeated repository
rules, keyword catchalls, and model-specific scaffolding.
Preserve the user's scope and existing authorization. Continue through
authorized implementation and verification; ask only for missing decisions.
A skill being loaded does not itself authorize external writes or new work.