Ast Grep

What it does

When your agent uses it

• Code shape and element relationships matter
• Tasks that involve Codebase onboarding

Example prompts

• “find async functions without error handling”
• “refactor foo(a, b) to foo({ a, b })”
• “/ast-grep”

Workflow steps

4 steps, taken from the first numbered list in SKILL.md.

1. 1Write a test snippet representing the target code
2. 2Write the rule (start with pattern, escalate to kind + has/inside if needed)
3. 3Test with --stdin before searching the codebase
4. 4Search the codebase once the rule matches

What it can do on your machine

Read from SKILL.md and the folder at commit 82d2921. 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 and yaml).

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

• Network

  No URLs in SKILL.md.

  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 531 tokens when it runs, and up to ~3.8k if it reads all its reference files. Until then it costs about 60 tokens; SKILL.md has 156 words of instructions outside code blocks.

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

~60

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

~531

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

~3.8k

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 poteto/noodle at commit 82d2921, republished under its MIT licence (© poteto). 156 words, ~531 tokens.

name

ast-grep

description

Structural code search via ast-grep — use when code shape and element relationships matter, not just text. E.g., "find async functions without error handling", "refactor foo(a, b) to foo({ a, b })". Use Grep for simple name lookups.

# WRONG — will miss deeply nested matches
has:
  pattern: await $EXPR

# RIGHT
has:
  pattern: await $EXPR
  stopBy: end

# Double-quoted: escape with backslash
ast-grep scan --inline-rules "id: test
language: javascript
rule:
  pattern: await \$EXPR" .

# Single-quoted: no escaping needed
ast-grep scan --inline-rules 'id: test
language: javascript
rule:
  pattern: await $EXPR' .

echo "async function test() { await fetch(); }" | ast-grep scan --inline-rules 'id: test
language: javascript
rule:
  kind: function_declaration
  has:
    pattern: await $EXPR
    stopBy: end' --stdin

ast-grep run --pattern 'your code here' --lang javascript --debug-query=cst

© poteto, 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 1 other file (references) in .agents/skills/ast-grep of poteto/noodle.

• SKILL.md
• references/rule_reference.md

Open the folder on GitHubat commit 82d2921