i18n-locale-mcp

A zero-dependency MCP server that gives any AI agent a localization QA toolkit. Deterministic, offline-capable, and safe to run in CI.

Works with Claude Desktop, Cursor, Dify, AutoGPT, and any MCP-compatible client.

Why

Shipping a product in 20 locales is easy; shipping it correctly is not. Agents and devs constantly produce 1,234 in German, 03/25 in French, missing {name} placeholders, or untranslated brand terms. This server catches those deterministically — no API key needed.

Related MCP server: i18n Agent

Tools

localize never fabricates translations: without a provider configured it returns machine-readable translation jobs (source + rules + placeholders) for you to execute.

Install

git clone <repo> && cd i18n-mcp
node index.js --list-tools     # sanity check
node test/smoke.mjs            # 11 deterministic checks

Requires Node.js >= 18. No dependencies.

Use with an MCP client

Add to claude_desktop_config.json (or Cursor / Dify MCP settings):

{
  "mcpServers": {
    "i18n": {
      "command": "node",
      "args": ["/absolute/path/to/i18n-mcp/index.js"]
    }
  }
}

Optional: enable live translation

Set an OpenAI-compatible endpoint and localize will translate before linting:

export I18N_LLM_BASE_URL="https://api.openai.com/v1"
export I18N_LLM_API_KEY="sk-..."
export I18N_LLM_MODEL="gpt-4o-mini"      # optional

Without these, localize returns providerMode: "jobs" and does zero network calls.

Examples

Pseudolocalize (find hard-coded UI strings)

pseudoLocalize("Save changes")   // 【Såvé çhångéš~~~~~~~~~】

Lint a translation

{ "text": "Gesamt: 1,234 EUR", "locale": "de-DE" }

→ NUMBER_GROUP_SEP error: German expects . as thousands separator.

Programmatic API

import { pseudoLocalize, lint, glossaryApply, localize } from "i18n-locale-mcp";

lint("Cherchez 03/25/2026", "fr-FR");                       // DATE_ORDER error
glossaryApply([{ source: "Save", target: "Enregistrer" }],
              [{ key: "btn.save", text: "Save" }]);          // TERM_UNTRANSLATED
await localize("Hello {name}", ["de-DE", "ja-JP"]);          // lint-ready output

CLI

node index.js              # run MCP server on stdio
node index.js --list-tools # list tools
node index.js --version

License

MIT