unicode-le-mcp

unicode-le-mcp

An MCP server that finds the Unicode risks in a document — the characters that hide meaning: bidirectional controls, invisibles, homoglyphs, words that mix scripts, text that is not in NFC — the detection engine behind the Unicode-LE editor extension, exposed as a tool an agent can call.

It reports codepoints as U+XXXX and never returns the characters themselves. A model that pasted a document into its own reasoning has already been handed the bidi controls in it; what comes back from here cannot carry them on into a commit message or a review comment. Every non-ASCII character in a reply leaves as a \uXXXX escape, including the key paths, which are text from the document.

No dependencies, no network calls, no filesystem access. Content goes in, structured results come out.

Use it

Point any MCP host at npx unicode-le-mcp.

Claude Code

claude mcp add unicode-le -- npx -y unicode-le-mcp

Anything with a JSON config — Cursor, Windsurf, Claude Desktop:

{
  "mcpServers": {
    "unicode-le": {
      "command": "npx",
      "args": ["-y", "unicode-le-mcp"]
    }
  }
}

VS Code needs nothing here. Install the extension instead — it carries this server and registers it for you: VS Code Marketplace · Open VSX

No Node? The same detect_unicode_risks tool ships in a static Rust binary: cargo install unicode-le, then unicode-le mcp (crates.io). The two servers answer identically — one corpus runs against both, a differential test feeds both thousands of generated documents and compares every answer, and both read the same Unicode tables, written out by the crate, rather than whatever version the host's JavaScript engine carries. The binary additionally offers unicode_le_scan, which walks a tree; this server reads no files.

Prefer a global install to npx on every launch:

npm install -g unicode-le-mcp

{
  "mcpServers": {
    "unicode-le": { "command": "unicode-le-mcp" }
  }
}

No environment variables, no API key, no configuration of its own. To check it before wiring it into anything:

echo '{"jsonrpc":"2.0","id":1,"method":"tools/list"}' | npx -y unicode-le-mcp

If that prints the tool name, the server works.

The tool

detect_unicode_risks

argument	type
content	string	required. The document text to scan.
kinds	string[]	Report only these: bidi, invisible, confusable, mixed-script, non-nfc, whitespace, unassigned. Omit for all of them — the only setting under which an empty result means clean.
scripts	string[]	Non-Latin scripts the document is expected to be written in, by Unicode name or ISO 15924 tag: Han, Cyrillic, Hira. Naming them lets the homoglyph check run on a translated document.
format	string	json, yaml, toml, ini, env, csv, tsv or text, so each finding can carry the key path it sits under.
filename	string	An alternative to format; only its extension is read.
maxResults	number	Default 500, ceiling 5000.

Each finding carries its kind, severity, 1-based line and column (UTF-16, as an editor counts), byte offset, the codepoints, the script and, where the format allows, the key path:

{
  "ok": true,
  "data": {
    "findings": [
      {
        "kind": "confusable",
        "severity": "high",
        "line": 2,
        "column": 8,
        "offset": 70,
        "key": "auth.provider",
        "codepoints": ["U+0430"],
        "scripts": ["Cyrillic"],
        "resembles": ["U+0061"],
        "detail": "a Cyrillic character in a word that is not Cyrillic, and it reduces to the codepoint under `resembles`: the two are indistinguishable on screen"
      }
    ],
    "refusals": []
  },
  "diagnostics": [],
  "meta": { "tool": "detect_unicode_risks", "count": 1, "truncated": false }
}

A document plainly written in a script nobody declared is refused for the homoglyph and mixed-script checks rather than judged by them. The refusal comes back twice — in data.refusals and as a warning diagnostic — so an empty finding list is never mistaken for a clean document. ok means the check ran, not that the answer was yes.

Also in the MCP registry

io.github.nolindnaidoo/unicode-le — registry.modelcontextprotocol.io

Ten more like it

One tool each, same shape: content in, structured data out, no network and no filesystem. Every one is on npm as <name>-mcp and in the MCP registry as io.github.nolindnaidoo/<name>.

Package	Tool	Does
urls-le-mcp	extract_urls	URLs, with protocol and position
colors-le-mcp	extract_colors	colors from stylesheets and code
dates-le-mcp	extract_dates	dates and timestamps
numbers-le-mcp	extract_numbers	numeric values
paths-le-mcp	extract_paths	file and directory paths
string-le-mcp	extract_strings	string values
regex-le-mcp	extract_patterns	regexes, with a ReDoS verdict
secrets-le-mcp	detect_secrets	credentials, masked — never the value
envsync-le-mcp	compare_env_files	dotenv key drift, names only
scrape-le-mcp	analyze_robots_txt	whether a path may be crawled

Every tool in the family, one page: letools.dev

Built by

Nolin Naidoo — Chief Engineer, AI/ML & Platform Architecture. nolindnaidoo.com · GitHub · LinkedIn

Also from the same workshop

Twelve Rust tools built the same way: small, single-purpose, and driven by a machine rather than a person. pixelcoords and pixelactions make up one loop — pixelcoords answers where, pixelactions acts there. The ten LE crates are the terminal half of the extensions they sit in: the same detection, held to the extension's own corpus, and an exit code instead of a results editor.

pixelcoords	Freeze your screen, mark regions, get pixel-exact coordinates and crops	site · crates.io · docs.rs
pixelactions	Consume human-verified coordinates, perform the interaction, confirm it landed	site · crates.io · docs.rs
paths-le	Find every path in a codebase and report whether it still points at anything	crates.io
secrets-le	Find hardcoded credentials, and never print one	crates.io
urls-le	Extract every URL from a codebase, with its protocol and exact position	crates.io
regex-le	Find every regex in a codebase and report which can be driven into catastrophic backtracking	crates.io
string-le	Get every string in a codebase out where a person can read them	crates.io
numbers-le	Find every hardcoded number in a codebase so a person can check them	crates.io
envsync-le	Compare the dotenv files in a tree and say which keys are missing from which	crates.io
colors-le	Find every colour in a codebase, and say which are not in your palette	crates.io
dates-le	Extract every date and timestamp, and the exact instant each one resolves to	crates.io
scrape-le	Check whether a page is scrapeable before the scraper is written	crates.io

Licence

MIT © Nolin Naidoo