Bareun — Korean NLP & Spell/Grammar Checking

Bareun MCP Server — Korean NLP & Spell/Grammar Checking

바른(Bareun) is a Korean natural-language platform. This is its MCP (Model Context Protocol) server — it lets any MCP-compatible AI tool (Claude, Cursor, VS Code, Claude Desktop, …) perform Korean morphological analysis and spell/grammar correction by calling Bareun as a tool.

Large language models still miss the subtle spacing, particle agreement, and confusable-word rules of Korean. Plug Bareun in as an MCP tool and your agent can hand off analysis and proofreading to a dedicated Korean engine, then use the result to produce more accurate Korean output.

• Hosted endpoint: https://api.bareun.ai/mcp
• Transport: Streamable HTTP (JSON-RPC 2.0) — no SSE, no extra port, no install
• Auth: API key (api-key header or Authorization: Bearer <key>)
• Get an API key: https://bareun.ai

The /mcp endpoint is available on the spell-checker–included build of Bareun (the morphological-analysis-only build does not expose /mcp). The same endpoint works on self-hosted/on-prem installs — just swap the host.

---

What it looks like

Spelling & spacing — correct_grammar (real output from https://api.bareun.ai/mcp):

In	회의결과를 정리해서 내일까지 보내주시기 바람니다.
Out	회의 결과를 정리해서 내일까지 보내 주시기 바랍니다.

Every fix comes back as a block, so an agent can explain the edit instead of silently rewriting the sentence:

Original	Corrected	Category	Rule
회의결과를	회의 결과를	SPACING	compound noun spacing
보내주시기	보내 주시기	SPACING	auxiliary-verb spacing
바람니다.	바랍니다.	TYPO	misspelling

Morphological analysis — analyze_syntax (format: compact):

In	나는 학교에 간다.
Out	나/NP 는/JX 학교/NNG 에/JKB 가/VV ㄴ다/EF ./SF

Homograph senses — analyze_syntax with with_sense: true (beta): 배 in 배가 아프다 comes back with senseNo: 1 and its dictionary definition — 사람이나 동물의 몸에서 … 가슴과 엉덩이 사이의 부위 (belly, probability 0.87), plus the Urimalsaem entry id — so the agent knows which 배 it is reading.

---

Tools

Tool	What it does	Key inputs
analyze_syntax	Splits a sentence into words/morphemes and tags parts of speech (morphological analysis).	text (required), auto_split_sentence, auto_spacing, auto_jointing, custom_dict_names, encoding, format (full|compact), with_sense
analyze_syntax_raw	Same analysis without post-processing (no compound-noun/verb splitting, no auto spacing, no custom dictionaries) — the raw model output.	text (required), auto_split_sentence, encoding, format, with_sense
search_dict	Searches the Urimalsaem Korean dictionary (~1.1M entries) by jamo (phoneme-level) slot patterns — conditions like "verbs whose stem ends in the ㅎ coda" or "words ending in -아지" that cannot be expressed with composed Hangul syllables.	pattern (required), anchor (word|prefix|suffix|contains), pos, std_only, with_definition, limit, count_only
tokenize	Splits a sentence into word (token) units.	text (required), auto_spacing, encoding
correct_grammar	Corrects spelling/spacing and returns correction blocks.	text (required), custom_dict_names, + 9 boolean correction options
list_pos_tags	Returns the 47 part-of-speech tags Bareun uses (code · name · class).	(none)

correct_grammar options (all boolean, default off): treat_as_title, disable_split_sentence, disable_caret_spacing, disable_vx_spacing, enable_limited_punctuation, disable_confusion, enable_cleanup_whitespace, disable_typo_correction, enable_sentence_check.

encoding controls the unit for morpheme offsets: utf32 (default, code points — matches Python), utf16 (JS/Java), utf8 (bytes — Go/C++).

with_sense — homograph sense disambiguation (WSD, beta). Korean writes many unrelated words identically: 배 can be belly, ship, or pear. Set with_sense: true on analyze_syntax/analyze_syntax_raw and each content morpheme carries a sense object — the dictionary sense number, its Korean definition, the Urimalsaem entry id, and the probability of the chosen sense among that word's candidate senses. It is off by default (one extra model pass; responses are byte-identical to before when omitted), and format=compact renders it inline as 배__002/NNG. This feature is in beta and ships officially with Bareun 3.1.0.

Resources

Resource URI	Contents	Auth
bareun://pos-tags	The 47 POS tags (code · name · class) — same data as list_pos_tags	API key
bareun://server-info	Server metadata — name · version · build · active tools/resources	API key
bareun://custom-dicts	Names of custom-dictionary domains registered for the key	valid API key

---

Quick start

Tip — register globally. Most tools default to project scope (the server is only available in one project). To use Bareun across all your projects, register it at global / user scope as shown below.

Claude Code

# -s user → global: available in every project
claude mcp add -s user --transport http bareun https://api.bareun.ai/mcp \
  --header "api-key: YOUR_API_KEY"

Omit -s user for project-local scope. Check with claude mcp get bareun.

Cursor

Global: ~/.cursor/mcp.json · Project: <project>/.cursor/mcp.json

{
  "mcpServers": {
    "bareun": {
      "url": "https://api.bareun.ai/mcp",
      "headers": { "api-key": "YOUR_API_KEY" }
    }
  }
}

VS Code

Global: run MCP: Open User Configuration · Project: <project>/.vscode/mcp.json

{
  "servers": {
    "bareun": {
      "type": "http",
      "url": "https://api.bareun.ai/mcp",
      "headers": { "api-key": "YOUR_API_KEY" }
    }
  }
}

Claude Desktop — claude_desktop_config.json

Claude Desktop bridges header-authenticated remote servers via mcp-remote (Node.js required):

{
  "mcpServers": {
    "bareun": {
      "command": "npx",
      "args": [
        "-y", "mcp-remote",
        "https://api.bareun.ai/mcp",
        "--header", "api-key: YOUR_API_KEY"
      ]
    }
  }
}

Cline — cline_mcp_settings.json

Open MCP Servers → Configure MCP Servers in Cline, then add:

{
  "mcpServers": {
    "bareun": {
      "type": "streamableHttp",
      "url": "https://api.bareun.ai/mcp",
      "headers": { "api-key": "YOUR_API_KEY" },
      "disabled": false,
      "autoApprove": []
    }
  }
}

All five tools are read-only (readOnlyHint), so listing them in autoApprove is safe if you would rather not confirm every call.

ChatGPT — Developer Mode

ChatGPT talks to Streamable HTTP servers directly — no directory review needed. Turn on Developer mode (Settings → Apps & Connectors → Advanced), then Create a connector:

• URL: https://api.bareun.ai/mcp
• Authentication: OAuth — Bareun runs its own OAuth 2.1 (PKCE) endpoint, so ChatGPT opens a login page where you paste your Bareun API key. (ChatGPT's connector dialog offers OAuth or no-auth; if your build also lets you set request headers, an api-key header works just as well.)

Menu wording and plan availability shift between ChatGPT releases — Developer mode is an account-level toggle, and on Business/Enterprise a workspace owner enables it first.

Test with MCP Inspector

npx @modelcontextprotocol/inspector

Set Transport to Streamable HTTP, URL to https://api.bareun.ai/mcp, and add header api-key: YOUR_API_KEY.

---

Example

// tools/call → analyze_syntax  (format: compact)
{ "text": "나는 학교에 간다.", "format": "compact" }
// → "나/NP 는/JX 학교/NNG 에/JKB 가/VV ㄴ다/EF ./SF"

Links

• Service: https://bareun.ai
• Docs: https://bareun.ai/docs
• MCP guide: https://bareun.ai/docs/howtouse/mcp
• API keys & usage: https://bareun.ai/docs/howtouse/cloud-api

License

The contents of this repository (documentation, registry manifests, examples) are released under the MIT License. The Bareun engine itself is a proprietary service operated by Baikal AI; access is governed by the bareun.ai terms of service.