MCP Issues

This page covers the VULK MCP server in both forms: the npm package that uses an API key, and the remote connector you add by address and sign in to. The sections marked (sign-in) are about the connector; the others are about the package. Setup for both is in MCP Integration.

"This request is no longer valid" (sign-in)

The approval screen expired, was already answered, or was opened with a different VULK account. Go back to your assistant and start the connection again.

"Connection limit reached" (sign-in)

Your VULK account already has the maximum number of connected apps (50) or unanswered approval screens (20). Remove an app you no longer use, or wait a few minutes for unanswered ones to expire, then start the connection again from your assistant.

Your assistant asks you to sign in again (sign-in)

A connection lasts 90 days at most, and ends sooner if you remove the app. Approve it again from your assistant.

"This connection was not granted the projects.write permission" (sign-in)

The app was connected with read access only. Remove it in Settings › Integrations › Connected apps, then connect it again and approve the screen that lists Create and change your projects.

"VULK could not admit this operation … (HTTP 402)" (sign-in)

Your plan or credit balance cannot cover the request. Check Settings › Billing, then ask your assistant again.

A build never shows a receipt (sign-in)

If the answer says unconfirmed, VULK had not confirmed the request within about 20 seconds. Ask your assistant to read it with get_operation. If there is still no receipt, it should retry with the same request_id and the same arguments instead of starting another request.

"VULK_API_KEY not set"

The MCP server requires a VULK_API_KEY environment variable. Make sure your editor config includes the env block:

{
  "mcpServers": {
    "vulk": {
      "command": "npx",
      "args": ["-y", "vulk-mcp-server"],
      "env": {
        "VULK_API_KEY": "vk_sk_your_key_here"
      }
    }
  }
}

Get your key from vulk.dev/settings/api-keys.

"Unauthorized" (401) Errors

• Your API key may have been revoked — create a new one in Settings > API Keys
• Verify the key starts with vk_sk_
• Check there are no extra spaces or line breaks in the key

MCP Server Not Starting

Node.js version

Requires Node.js 18 or later. Check with node --version.

npx not found

Ensure npm/npx is installed and in your PATH. Try running npx -y vulk-mcp-server directly in a terminal.

Firewall blocking

The MCP server connects to https://vulk.dev/api/v1/. Ensure outbound HTTPS is allowed.

Tools Not Appearing

After configuring the MCP server, restart your editor completely. Some editors (Claude Desktop, Cursor) need a full restart to pick up new MCP configurations.

Generation Timeout

Large projects may take up to 2 minutes to generate via MCP. If the tool times out, check the project in the VULK web editor — generation may still be running.

Rate Limit Errors

MCP requests follow the same rate limits as the VULK API. If you hit limits, wait for the retryAfter period indicated in the error response.