Shipi18n MCP Server

Shipi18n

Catch broken translations before you ship them. An open-source QA gate for your locale files — and, when you want it, an i18n translation engine that runs on your own LLM key.

Your es.json says Hola where the English says Hello {{name}}. The placeholder is gone, the build is green, and the bug ships. Shipi18n finds that, and it finds the harder kind too: the string that has every placeholder and still says the wrong thing.

A real run, not a mockup — docs/check-demo.tape reproduces it.

npx @shipi18n/cli check ./locales -s en

No API key, no account, no config. Missing keys, dropped placeholders, collapsed plurals, empty values and untranslated copy — as human output, JSON, SARIF (GitHub PR annotations) or JUnit.

If the check catches something in your project, consider starring the repo — stars are how the next person with a broken es.json finds this.

Then, when you want the meaning checked, bring your own key. The judge needs a provider SDK alongside the CLI:

npm i -D @shipi18n/cli @anthropic-ai/sdk       # or `openai`
export ANTHROPIC_API_KEY=sk-ant-...            # or OPENAI_API_KEY
npx shipi18n check ./locales -s en --semantic

An LLM reads each pair and reports mistranslations, omissions and additions:

⚠ es  coverage 100.0%  0 error(s), 1 warning(s)
    warning  delete  semantic-mistranslation — Translation says 'will save' (guardará)
                     instead of 'will delete' (eliminará/borrará)

Every placeholder is intact and every key is present, so structural checks pass this file. Only reading it catches the bug. Advisory by default — it warns, it does not fail your build.

Measured, not asserted. On a 228-pair corpus committed before the judge was written (60d699b) and with thresholds fixed first: 54/54 planted errors caught (100%) and 12/168 false positives on clean pairs (7.1%), with 6/6 glossary violations found. Reproduced on two independent runs (2026-08-16 and 2026-08-17) using claude-haiku-4-5, 3 passes, ~59k tokens in 156s. Label accuracy moved between runs (100% → 98.1%) — it is a model, so read these as a range, not a constant. The harness is evals/semantic/. Run it against your own model.

Nothing goes through our servers, because there are none. The only network call is from your machine to the provider you chose.

Packages

Why

Generating translations is a solved problem. Half a dozen good tools will fill your locale files, and an agent will do it for free. Nothing checks the result. Your CI lints your JavaScript, typechecks your types and runs your tests — and then ships a de.json that nobody has read, produced by a model nobody audited.

The checks that do exist are structural: they diff key sets and stop there. That catches the missing key. It does not catch the translation that has every key and every placeholder and still tells your German users the opposite of what you meant.

Shipi18n is that missing gate, in two layers:

• Deterministic, offline, no key. Missing and orphaned keys, dropped or malformed placeholders ({{name}}, {count}, %s, %d, %1$s, $t(...), %{name}, HTML), collapsed plural forms, empty values, untranslated copy, coverage per language.
• Semantic, with your own key. An LLM-as-judge pass over changed keys only, with multi-pass majority voting because single-pass judge scores are unstable. Reports mistranslation, omission and addition. Advisory by default — a QA tool that fails your build gets uninstalled.

Plus the parts that make it usable day to day:

• Formats beyond JSON. YAML (.yaml/.yml), Flutter .arb and Apple .xcstrings, including %@/%lld specifiers.
• CI-native. Correct exit codes, --fail-on, --min-coverage, SARIF for PR annotations, JUnit.
• Hand-edits are protected. shipi18n lock records the translations a human blessed and warns when anything overwrites them, or when the source moves underneath them.
• Keyless from your editor. The MCP server's validators call no model at all.
• It also translates. Provider-agnostic, structure-preserving, incremental — Anthropic and OpenAI in the box, and any object with a complete(prompt) method is a valid adapter.

Check from your editor — no API key

@shipi18n/mcp brings the checks to any MCP client. The validation tools call no model, so they need no key at all.

Claude Code — one line:

claude mcp add shipi18n -- npx -y @shipi18n/mcp

Claude Desktop / any MCP client — paste the config:

// claude_desktop_config.json
{
  "mcpServers": {
    "shipi18n": { "command": "npx", "args": ["-y", "@shipi18n/mcp"] }
  }
}

"Check ./locales against English and tell me what's broken in Spanish."

review_locales goes further without needing a key either: it hands your agent the translation pairs and the review criteria, and your agent reasons about meaning with the model it already runs.

Check in CI — no key needed

The checks work on translations from any source — a TMS, another tool, an agent, a human. Run it on every push:

npx @shipi18n/cli check ./locales -s en

Missing keys, dropped placeholders, collapsed plurals, empty values and untranslated copy — reported as human output, JSON, SARIF (GitHub PR annotations) or JUnit. Works on plain JSON trees, Flutter YAML, .arb bundles and Apple .xcstrings catalogs. Deterministic and offline: no LLM, no API key.

Protect hand-edited translations

Fix a string by hand, lock it, and check warns you if anything ever overwrites it — or if the English moves underneath it:

npx @shipi18n/cli lock ./locales --keys 'legal.*'

.shipi18n/locks.json stores hashes only, is safe to commit, and these findings are warnings — protecting human work must never block a pipeline. Details in the CLI README.

It also translates

Checking works on translations from anywhere, but if you want Shipi18n to produce them too, it does — with your key, your model, and nothing in between.

npm i -D @shipi18n/cli @anthropic-ai/sdk       # or `openai`
export ANTHROPIC_API_KEY=sk-ant-...            # or OPENAI_API_KEY
npx shipi18n translate locales/en.json -t es,fr,de

✔ es → locales/es.json (2 translated, 0 reused)

Or from Node (same SDK requirement):

import { translateJSON } from '@shipi18n/core'

const { result, stats } = await translateJSON({
  content: { greeting: 'Hello {{name}}' },
  from: 'en',
  to: 'es',
  provider: 'anthropic',        // 'anthropic' | 'openai' | custom { complete } adapter
})
// result → { greeting: 'Hola {{name}}' }

Structure-preserving, placeholder-safe and incremental — only new or changed keys are sent to the model. Then check the result with the same tool.

Development

This is a pnpm + turbo monorepo.

pnpm install
pnpm test          # all packages
pnpm --filter @shipi18n/core test

Changesets manage versioning: pnpm changeset to add one.

Contributing

Issues and pull requests are welcome — see CONTRIBUTING.md. pnpm install && pnpm test runs 105 tests against a mock adapter, so you need no API key to work on this.

License

Apache-2.0 © Shipi18n. See NOTICE.