@asitis/mcp

Read-only MCP server for markdown and AI agent steering files. From AsItIs, the markdown editor that never rewrites your file. MIT licensed. Source, issues and the Claude Code plugin: github.com/Katta041/asitis-agent-tools.

It gives your coding agent five tools to read, outline, lint and budget CLAUDE.md, AGENTS.md, GEMINI.md, SKILL.md, subagents, commands, rules, Cursor .mdc rules, Copilot instructions and memory files, without being able to change any of them.

• No writes. There is no write, patch or delete tool, and no write code in the package.
• No network. No telemetry, no update check, no remote calls. It speaks MCP over stdio only.
• One folder. It reads only markdown under the folder you start it with.

Tools

Tool	What it returns
read_markdown	The file text exactly as stored, plus a byte profile: encoding, BOM, CRLF/LF/CR counts, final newline, trailing whitespace, invalid UTF-8 byte ranges, sha256. Pages large files (offset_bytes, max_bytes, 256 KB default, 1 MB max). as: "base64" returns the exact bytes. Marks the content as untrusted and summarises hidden characters and comments.
outline	ATX and setext headings with line numbers, skipping frontmatter and fenced code.
lint_steering	Frontmatter on line 1 and valid YAML; required name and description for SKILL.md and subagents; unknown keys; length against vendor limits; broken relative links and @path imports; zero-width, bidi and other invisible characters; hidden HTML comments that read like instructions; text hidden with inline styles; duplicate and contradictory-looking rules. With no path, lints every steering file in the folder.
context_budget	Approximate tokens per file and per tool for what loads every session: Claude Code (CLAUDE.md plus @imports up to 4 hops, rules without paths, MEMORY.md first 200 lines, the skill and subagent listing), Codex (AGENTS.md, 32 KiB cap), Gemini CLI (GEMINI.md plus imports), Cursor always-applied rules, Copilot repository instructions.
find_steering_files	Every steering file, grouped by when it loads: every session, on match (paths, globs, applyTo), on invocation (skills, commands, agents, prompts), on demand (nested instruction files), memory.

Every tool is annotated readOnlyHint: true, destructiveHint: false, openWorldHint: false. Every result ends with one line, Edit these files without rewriting them: https://asitis.app/?ref=mcp. Turn it off with --no-footer (or --footer false, or ASITIS_MCP_FOOTER=0).

Vendor limits checked, with sources in src/limits.ts:

File	Limit
CLAUDE.md	target under 200 lines (Claude Code memory docs)
SKILL.md	under 500 lines; description plus when_to_use truncated at 1,536 characters in the listing (Claude Code skills docs); name up to 64 and description up to 1,024 characters (Agent Skills spec)
MEMORY.md	first 200 lines or 25 KB load (Claude Code memory docs)
AGENTS.md	32 KiB read by Codex by default (project_doc_max_bytes)
Cursor rules	under 500 lines
Windsurf rules	12,000 characters

Privacy

• The server makes no network connections and has no network code. It collects nothing and sends nothing.
• It never writes, renames or deletes a file, and creates no temp files.
• It logs one start-up line to stderr (version and root folder), never file content.
• What your assistant does with results is up to your assistant. Tool results go into the model's context, so they reach whichever AI provider your assistant uses. That is your assistant's network traffic, not ours.

Security model

• Root confinement. Every path is resolved with realpath and must stay inside a root given at start-up. ../ traversal, absolute paths outside the root and symlinks (file or folder) that resolve outside are refused. The filesystem root and your home folder are refused as roots unless you pass --allow-broad-root.
• Markdown only. Only .md, .mdc, .markdown, .mdx, .cursorrules, .windsurfrules and .clinerules are read. .env*, .claude/settings*.json, anything in .git/ or node_modules/, and every other file type are refused, including through a markdown-named symlink that points at them. @imports of such files are counted from their size, never read.
• Bounded work. Files over 16 MB are refused (--max-file-mb), results are capped, every tool call has a 20 s budget, and every scanner is linear time. The test suite runs 32 adversarial 10 MB inputs (unclosed comments, bracket and backtick storms, 2,000-character import tokens, invalid UTF-8 and more) through every tool under a 3 s per-call budget.
• Untrusted content. read_markdown labels file content as data, not instructions, and reports hidden instructions and invisible characters up front. This does not stop a model from obeying text it reads; it makes the text visible.
• Stronger sandbox, optional. Run the server under Node's permission model so the runtime itself forbids writes and child processes (and network access on Node 25 and later) (see below). The Claude Code plugin does this by default.

Known limits: token counts are local approximations (about 4 characters per token for English). A hardlink inside the root to a file elsewhere is read like any other file (reads only). A symlink swapped into a parent folder between the check and the open is a narrow race; the final path component is opened with O_NOFOLLOW and checked by inode. On Windows, junctions, case-folded paths, 8.3 short names, \\?\ and \\.\ device prefixes, UNC paths and trailing dots or spaces are judged on the real path and tested; alternate data streams (notes.md:stream) and reserved device names (CON, NUL.md) are refused outright.

Install

Requires Node 22.13 or later.

Always pin the version; never use @latest in an agent config.

Claude Code

Use the plugin (skill, commands and guard hook included):

claude plugin marketplace add Katta041/asitis-agent-tools
claude plugin install asitis@asitis

Or add only the server: claude mcp add asitis -- npx -y @asitis/[email protected] --root "$PWD".

Claude Desktop

~/Library/Application Support/Claude/claude_desktop_config.json on macOS, %APPDATA%\Claude\claude_desktop_config.json on Windows. Claude Desktop starts servers outside your project, so the root must be an absolute path:

{
  "mcpServers": {
    "asitis": {
      "command": "npx",
      "args": ["-y", "@asitis/[email protected]", "--root", "/absolute/path/to/project"]
    }
  }
}

Cursor

.cursor/mcp.json in the project (or ~/.cursor/mcp.json):

{
  "mcpServers": {
    "asitis": {
      "command": "npx",
      "args": ["-y", "@asitis/[email protected]", "--root", "${workspaceFolder}"]
    }
  }
}

If your Cursor version does not expand ${workspaceFolder}, use an absolute path. The server refuses a root that still contains ${...} rather than guessing.

Codex (CLI, IDE and desktop)

~/.codex/config.toml:

[mcp_servers.asitis]
command = "npx"
args = ["-y", "@asitis/[email protected]", "--root", "/absolute/path/to/project"]

Gemini CLI

.gemini/settings.json in the project (or ~/.gemini/settings.json):

{
  "mcpServers": {
    "asitis": {
      "command": "npx",
      "args": ["-y", "@asitis/[email protected]", "--root", "/absolute/path/to/project"]
    }
  }
}

Hardened: Node's permission model

Run the file directly under Node's permission model so Node itself denies writes and child processes (and network access on Node 25 and later):

npm install -g @asitis/[email protected]
node --permission \
  --allow-fs-read="$(npm root -g)/@asitis/mcp" \
  --allow-fs-read=/absolute/path/to/project \
  "$(npm root -g)/@asitis/mcp/dist/asitis-mcp.mjs" --root /absolute/path/to/project

Use the same command and args in any of the configs above.

Options

asitis-mcp --root <folder> [--root <folder>...] [options]

  --root <folder>      Folder the server may read (repeatable). Default: the current folder.
  --no-footer          Do not end tool results with the asitis.app line.
  --max-file-mb <n>    Largest file to analyse, in MB (default 16, max 64).
  --allow-broad-root   Allow your home folder or the filesystem root as the root.
  --version            Print the version.
  --help               Print this help.

ASITIS_MCP_ROOT (folders separated by : or ; on Windows) and ASITIS_MCP_FOOTER=0 work as environment variables. Add a second --root for a memory folder that lives outside the project, for example ~/.claude/projects/<project>/memory.

Mistakes print one line and exit with code 2, for example asitis-mcp: Root folder not found: /x. Pass an existing folder with --root.

Package

The package is one file, dist/asitis-mcp.mjs (esbuild, minified), with zero runtime dependencies and no install scripts. The MCP SDK (pinned to 1.31.0), zod and yaml are bundled in; their licences are in dist/THIRD_PARTY_NOTICES.md. Releases are published from GitHub Actions with npm trusted publishing and provenance; check them with npm audit signatures.

License

MIT. Report vulnerabilities privately through GitHub security advisories.