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ast-mcp

ast-mcp is a skill for Codex from mwillbanks/ast-mcp. It costs 57 tokens per session (1,115 once invoked), scanned A, original, MIT.

A code-exploration and file-management tool that understands source code structure and controls how files are read or changed.

In plain words
What is it for?
Finding symbols, mapping files, checking dependencies, reading and hashing files, creating files, and patching existing code.
Why use it?
It gives agents a consistent way to inspect unfamiliar code, trace relationships, and make edits while enforcing specific write rules.

Skill for Codex

Written for Codex: agents/openai.yaml present. Also seen: $skill-name invocation.

not rated 0repo changed 2d ago A scan 57 tokens original MIT

Good fit Finding symbols, mapping files, checking dependencies, reading and hashing files, creating files, and patching existing code.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/mwillbanks/ast-mcp/ast-mcp
View source ↗ mwillbanks/ast-mcp mwillbanks.github.io
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.

Any agent
npx skills add mwillbanks/ast-mcp --skill ast-mcp
Clone the repo
git clone --depth 1 https://github.com/mwillbanks/ast-mcp

Made for: Codex.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for ast-mcp

README.md
[![agentmods](https://agentmods.dev/badge/skills/mwillbanks/ast-mcp/ast-mcp/github.svg)](https://agentmods.dev/skills/mwillbanks/ast-mcp/ast-mcp)
Your own site
<a href="https://agentmods.dev/skills/mwillbanks/ast-mcp/ast-mcp"><img src="https://agentmods.dev/badge/skills/mwillbanks/ast-mcp/ast-mcp/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for ast-mcp

Your own site · 80×15
<a href="https://agentmods.dev/skills/mwillbanks/ast-mcp/ast-mcp"><img src="https://agentmods.dev/badge/skills/mwillbanks/ast-mcp/ast-mcp.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 57 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,115 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
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 5.1 $0.00057 $0.01115
Opus 5.5 $0.00023 $0.00446
Sonnet 5.5 $0.00011 $0.00223
Haiku 4.5 $0.00006 $0.00112

Measured 2d ago against content hash 58a8923c0f26, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

ast-mcp 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.

The scan reads SKILL.md. This mod also ships 13 executable files (evals/measure.ts, evals/score.test.ts, evals/score.ts, …), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

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.

templates/skills/ast-mcp/SKILL.md · 89 lines

How it starts

The opening of the file, as written. The whole thing — 89 lines — stays where its author put it; the contents beside it link to each section on GitHub.

AST MCP

Use AST-MCP for local files and local code intelligence. Use web or connector tools for remote content without local-file approval. Apply local file policy when you save remote content locally. Never use direct editors, shell writers, or interpreter writes to bypass this boundary.

Load the correct instructions

The host selects and activates the skill. For disk delivery, resolve relative links from the active skill directory, whether global or project-local. For MCP delivery, request each reference through its exact manifest URI. Do not invent a $ast-mcp/references/... filesystem path. Reading a resource does not activate a skill.

  • Load tool-catalog.md for tool inputs, workspace selection, indexing, retrieval, and graph operations.
  • Load patch-state-machine.md before file mutations or recovery from rejected patches.
  • Load installation.md for missing tools, disconnections, upgrades, stale instructions, or configuration migration.
  • Load configuration.md for path rules, approvals, formatting, telemetry, and CLI output.

Check availability

  1. Confirm that file tools and direct intelligence tools are callable.
  2. If tools are missing or disconnected, stop mutation and load the installation reference.
  3. Let the host reconnect the server, then verify discovery and a bounded read.
  4. Reinspect pending files after any connection failure. Never switch to another writer.

Explore local code

  1. Start unfamiliar work with digest. Use map for file structure and show for symbols.
  2. Use search or find_related for discovery, and context for nearby calls.
  3. Use impact before shared API changes. Use callers, dependencies, and graph tools to check affected code.
  4. Batch independent reads when schemas permit. Keep overlapping writes and dependent operations sequential.
  5. Keep native intelligence requests within one project root. Use absolute paths for linked worktrees.
  6. Use file_read with explicit mode when intent matters.
  7. Use source symbols, structured-document selectors, or bounded text ranges.
  8. Use document_query for bounded JSON, JSONC, TOML, and YAML values.

Read the full file on GitHub · 89 lines

Files

What ships with it

25 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

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 Changed · +2 lines 58a8923c0f26
  2. 4d ago Changed · -67 lines · -3 tokens per session 59a1fccaa2f3
  3. 1mo ago Changed · +11 lines 5478ba3e29b7
  4. 1mo ago First seen · 143 lines · 60 tokens per session scan A 1d83c76a1568

Subscribe to this mod's changes

ast-mcp is a skill published in the GitHub repository mwillbanks/ast-mcp (0 stars, last pushed 2d ago), licensed MIT. It adds 57 tokens to every session and 1,115 once invoked, about $0.0002 per session on Opus 5.5. 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.

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