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Langbly MCP server for AI translation

The Langbly MCP server lets an AI assistant translate text or HTML, detect a source language, and check supported languages through your existing Langbly account. It uses OAuth 2.1: you approve access in Langbly, so you never paste an API key into ChatGPT, Claude, or another MCP client.

For a product overview, see the Langbly MCP integration page.

{
  "transport": "streamable-http",
  "url": "https://mcp.langbly.com/mcp"
}
Rollout status

The production endpoint is being prepared for official OpenAI, Anthropic, and MCP Registry publication. Until launch, connecting may return an unavailable or not-found response. This page documents the frozen three-tool v1 contract.

What the Langbly MCP server does​

Langbly exposes three deliberately narrow tools. It does not give an AI client general access to your dashboard, API keys, billing details, files, translation memory, or account settings.

ToolPurposeChanges account usage?
translateTranslate one to 100 text or HTML stringsYes. Successful calls count input characters and may be billable.
detect_languageReturn the most likely language code and confidence for each textNo translation usage.
list_languagesReturn supported language codes and optional English namesNo translation usage.

The translate tool accepts a target language, an optional source language, plain text or HTML, formality, short context, translation instructions, an inline glossary, and a data-residency choice. The combined source limit is 100,000 characters. Results are capped below common MCP host response limits; split unusually large jobs into smaller batches.

For file-based or asynchronous document translation, use the Document Translation API. The first MCP version is intentionally limited to text/HTML translation and language utilities so its permissions are easy to understand and review.

Connect in three steps​

1. Create or open your Langbly account​

Create a Langbly account or sign in to your existing account. The connector maps your OAuth identity to that account. It never generates a hidden API key. If your signup is incomplete, finish account setup in Langbly before reconnecting.

2. Add the remote MCP URL​

In an MCP client that supports remote Streamable HTTP servers, add:

https://mcp.langbly.com/mcp

Once the official listings are live, prefer the verified Langbly Translation listing in OpenAI or Anthropic. A verified listing reduces the risk of authorizing an impersonating server. The canonical publisher is Langbly, and the official MCP Registry identifier is com.langbly/translation.

3. Approve OAuth access​

The client opens Langbly's consent screen. Check the client name, redirect host, requested scopes, and the notice that translation can consume account allowance or create billable usage. Approve only a client you recognize. Denying consent returns control to the client without granting access.

The requested identity scopes are openid, email, and profile. These scopes support sign-in and identity display; they do not give the connector access to your Langbly dashboard routes. MCP access tokens are audience-bound to https://mcp.langbly.com/mcp, while ordinary dashboard sessions use a separate audience and are rejected by the MCP resource.

Example requests​

You normally ask in natural language; the AI client selects the tool and builds the arguments. These examples show the underlying v1 inputs.

Translate text with strict EU processing​

{
  "texts": ["Your order has shipped."],
  "targetLanguage": "nl",
  "sourceLanguage": "en",
  "format": "text",
  "formality": "formal",
  "dataResidency": "eu"
}

dataResidency: "eu" selects Langbly's dedicated EU Translation Worker. The MCP Worker has separate service bindings for global and EU processing, so an EU request is never forwarded through the global provider chain. See EU data residency for the current regional design.

Translate HTML with terminology​

{
  "texts": ["<p>Start your free trial</p>"],
  "targetLanguage": "de",
  "format": "html",
  "instructions": "Keep the tone concise and suitable for a SaaS button.",
  "glossary": [
    { "source": "free trial", "target": "kostenlose Testphase" }
  ],
  "dataResidency": "global"
}

Langbly validates the input and routes it through the same translation, quality, quota, budget, caching, and usage pipeline as the public API. MCP is an additional authenticated interface, not a separate translation engine.

Detect a source language​

{
  "texts": ["Bonjour, comment allez-vous ?"],
  "dataResidency": "eu"
}

Short or ambiguous input can return und with low confidence. Detection is a utility result, not a guarantee about the language of sensitive or regulated content.

Billing and limits​

Only a successful translate tool call counts source characters toward the connected Langbly account. The same account entitlement, monthly allowance, spending cap, provider budget, and rate limits that protect API requests also apply to MCP. Langbly checks these controls before starting paid inference and returns a safe error when an account is disabled, incomplete, over its limit, or temporarily rate-limited.

Repeated translation calls are not treated as harmless reads: a retry can cause new usage. AI clients should therefore avoid automatically repeating a successful call. detect_language and list_languages are read-only and do not book translation characters.

For current commercial terms, included usage, and overage pricing, use the Langbly pricing page as the source of truth. The billing documentation explains how character usage is calculated.

Security and privacy​

The remote server uses the Model Context Protocol Streamable HTTP transport and Supabase OAuth 2.1 authorization code flow with PKCE. Tokens are signed with an asymmetric ES256 key and verified against the public JWKS endpoint. Langbly checks the exact issuer, resource audience, algorithm, user subject, account status, and OAuth client context before a tool can reach the Translation Worker.

Incoming OAuth tokens are not forwarded to translation providers. The MCP Worker sends only an internal account-bound request through a private Cloudflare service binding. No public internal bypass URL exists. Langbly does not store translation request bodies in its database; eligible results can be cached temporarily as explained in Caching. Operational records can include character counts, language pair, region, timing, outcome, and the mcp integration source, but not the source text itself.

The MCP client or host may retain your prompts, chat history, approvals, and tool results under its own privacy policy. Review that policy before sending personal, confidential, or regulated text. Langbly's own handling is described in the Privacy Policy and security documentation.

Revoke a connection​

Open Langbly Dashboard → Settings → Connected Applications, find the AI client, and select Disconnect. Langbly revokes that client's OAuth grant, sessions, and refresh access. The MCP service also checks the current Supabase session before every account-bound tool request, so a previously issued token cannot continue into the translation path after its session has been removed. The client must request consent again before it can reconnect.

The implementation follows the MCP authorization specification, RFC 9728 protected resource metadata, and Supabase's OAuth 2.1 server guidance.

Troubleshooting​

ResultMeaningWhat to do
401 unauthorizedToken is missing, expired, revoked, or for the wrong resourceReconnect the verified Langbly connector and complete OAuth again.
403 ACCOUNT_SETUP_REQUIREDOAuth succeeded, but no active Langbly account is linkedSign in to Langbly and finish account setup, then reconnect.
403 PERMISSION_DENIEDThe linked account is disabledContact Langbly support.
402 or account-limit errorAllowance or an account spending limit is reachedReview usage, billing, and spending caps in Langbly.
429Account or service rate/budget protection is activeRespect the retry delay and try later.
413Request or result is too large for the MCP pathSplit the text into smaller batches.
503Translation is temporarily disabled or an internal dependency is unavailableRetry later; include the response x-request-id if contacting support.

Frequently asked questions​

Do I need to paste a Langbly API key into ChatGPT or Claude?​

No. The official remote connector uses OAuth 2.1 and your existing Langbly account. Never paste an API key into a chat or unverified connector.

Can an MCP client access my Langbly dashboard or billing details?​

No. MCP OAuth tokens have a dedicated resource audience and are rejected by Langbly's dashboard routes. The three v1 tools expose only translation, detection, and the supported-language list.

Does translation through MCP cost more than the API?​

MCP uses the connected account's existing translation entitlement and billing pipeline. Consult the current pricing page for the applicable allowance and rates; the connector does not create a separate hidden subscription.

Can I keep processing inside the EU route?​

Yes. Set dataResidency to eu on translate or detect_language. The MCP Worker then calls only the dedicated EU Translation Worker binding.

Where can I verify the official server identity?​

Use the publisher Langbly, endpoint https://mcp.langbly.com/mcp, and MCP Registry name com.langbly/translation. Official directory links will be added to this page after publication. For help, contact hello@langbly.com or use the contact page.