Ast Grep

What it does

When your agent uses it

• Tasks involving YAML rules
• Tasks that involve Linting and formatting
• Tasks that involve Codebase onboarding

Example prompts

• “/ast-grep”

Workflow steps

12 steps, taken from the step headings in SKILL.md.

1. 1Understand the Query
2. 2Create Example Code
3. 3Write the ast-grep Rule
4. 4Test the Rule
5. 5Search the Codebase
6. 6Pattern Correctness (CRITICAL)
7. 7Meta Variable Usage (CRITICAL)
8. 8Rule Composition (HIGH)
9. 9Constraint Design (HIGH)
10. 10Rewrite Correctness (MEDIUM-HIGH)
11. 11Project Organization (MEDIUM)
12. 12Performance Optimization (MEDIUM)

What it can do on your machine

Read from SKILL.md and the folder at commit cf93c57. It shows what the files ask for, not the result of running them.

• Tool permissions

  Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

  From allowed-tools in the SKILL.md frontmatter.

• Runs code

  No scripts in the folder and no shell commands in SKILL.md (its code samples are bash).

  From the folder's file list and the shell code blocks in SKILL.md.

• Network

  Links to these hosts (documentation or services it may open):

  • ast-grep.github.io

  From URLs in SKILL.md, links to its own repository left out.

• Credentials

  Names no API keys, tokens, secrets or passwords.

  From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Ast Grep loads about 2.3k tokens when it runs, and up to ~19k if it reads all its reference files. Until then it costs about 71 tokens; SKILL.md has 708 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it

~71

When it runs · the whole SKILL.md, loaded when a task matches

~2.3k

With references · SKILL.md plus every file in references/, read only if the agent opens them

~19k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from pproenca/dot-skills at commit cf93c57, republished under its MIT licence (© pproenca). 708 words, ~2,322 tokens.

name

ast-grep

description

ast-grep rule writing and usage best practices. This skill should be used when writing, reviewing, or debugging ast-grep rules for code search, linting, and transformation. Triggers on tasks involving YAML rules, pattern syntax, meta variables, constraints, or code rewriting.

# Inspect AST structure
ast-grep run --pattern '[code]' --lang [language] --debug-query=ast

# Test inline rule
echo "[code]" | ast-grep scan --inline-rules "[rule]" --stdin

# Test from file
ast-grep scan --rule [file.yml] [path]

# Search with pattern (simple matches)
ast-grep run --pattern '[pattern]' --lang [language] [path]

# Search with rule file (complex queries)
ast-grep scan --rule [file.yml] [path]

# Apply fixes interactively
ast-grep scan --rule [file.yml] --interactive [path]

© pproenca, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

SKILL.md and 51 other files (references, assets) in skills/.experimental/ast-grep of pproenca/dot-skills.

• SKILL.md
• AGENTS.md
• README.md
• assets/templates/_template.md
• metadata.json
• references/_sections.md
• references/compose-all-for-and-logic.md
• references/compose-any-for-or-logic.md
• references/compose-field-targeting.md
• references/compose-has-for-children.md
• references/compose-inside-for-context.md
• references/compose-matches-for-reuse.md
• references/compose-not-for-exclusion.md
• references/compose-precedes-follows.md
• references/const-kind-filter.md
• references/const-not-inside-not.md
• references/const-pattern-constraint.md
• references/const-post-match-timing.md
• … and 34 more

Open the folder on GitHubat commit cf93c57