OpenCidian: open Chinese ↔ Vietnamese dictionary (Hán Việt, pinyin, character breakdown)

opencidian-mcp

A remote MCP server for OpenCidian by Perxel: an open Chinese-Vietnamese dictionary. It is the only public way in for systems: there is no public API. Read-only except suggest_correction, which opens a public GitHub issue for a maintainer (it never changes the data); no sign-in. A Cloudflare Worker built from the Perxel MCP Kit (kit/, see STANDARD.md) over opencidian-api, which is internal: it answers 404 to every read without X-MCP-Secret, which this Worker sends over its service binding.

opencidian-mcp (this repo) ──service binding──▶ opencidian-api ──▶ D1
  POST /mcp (Streamable HTTP, stateless)           loaded from opencidian-data's releases

GET / lists connect instructions and every tool; GET /llms.txt says what OpenCidian is, how to connect, example questions, licence and attribution (src/lib/llms.ts); /dash is a public usage dashboard. Host: opencidian-mcp.perxel.com.

Tools

Tool	Wraps	Notes
lookup	GET /v1/lookup	Hanzi, pinyin (with or without tones) or Vietnamese; by forces the reading, limit 1-50.
get_character	GET /v1/chars/{char}	Hán Việt, pinyin, radical, parts, etymology, strokes, traditional forms.
words_with	GET /v1/words-with/{char}	Words of 2+ characters containing it, HSK words first.
search_meaning	GET /v1/search	Vietnamese (default) or English meaning → candidate Chinese words.
annotate_text	POST /v1/annotate	Text (up to 2,000 characters) → words with pinyin, Hán Việt and meaning.
suggest_correction	POST /v1/corrections	Opens a public issue in opencidian-data (labels correction, from-ai); a maintainer turns it into a correction file. Never changes the data. 5 a minute for all MCP callers together.
about	GET /v1/meta	Version, licence, full attribution, sources with their pinned versions.

Every answer carries src per field, the dataset version and a short credit; the full attribution (every source) comes from about only, to keep answers small.

Setup

pnpm install
cp .dev.vars.example .dev.vars   # MCP_SECRET: the one in ../opencidian-api/.dev.vars
pnpm test && pnpm typecheck

Against a local opencidian-api: run wrangler dev there, then pnpm dev here. Against the deployed API: a temporary copy of wrangler.mcp.jsonc with "remote": true on the API service binding (never committed), then pnpm exec wrangler dev -c <copy> --port 8788.

Evals: pnpm eval --url http://localhost:8788/mcp (evals/questions.md).

Deploy

On push to main (.github/workflows/deploy.yml, repo secrets CLOUDFLARE_API_TOKEN and CLOUDFLARE_ACCOUNT_ID), or pnpm exec wrangler deploy -c wrangler.mcp.jsonc. Secrets: MCP_SECRET (same as opencidian-api's), IP_HASH_SALT, COOKIE_ENCRYPTION_KEY, DASH_PROXY_KEY (see wrangler.mcp.jsonc).

Licence

Code MIT (kit/ keeps the kit's own licence). Data CC BY-SA 4.0: credit "OpenCidian by Perxel" and its sources.