[Bug]: TypeError: connectionString.startsWith is not a function

[ImoutoChan]

Version

mcp/mongodb@sha256:44eed0f93b85db457e86d9a7de44aa032d6d9128aac05086194402adc4e2a9b7

App

• Cursor
• Windsurf
• VSCode
• VSCode Insiders
• Claude Desktop
• Other

Affected Models (if applicable)

• Claude 3.5 Sonnet
• Claude 3.7 Sonnet
• GPT-4a
• o4-mini
• Other

Bug Description

I'm trying to use docker desktop feature MCP Tools: https://docs.docker.com/ai/mcp-catalog-and-toolkit/toolkit/,
I installed mongodb and provided it with my connection string.

However, when I run docker mcp gateway run I get

docker mcp gateway run
- Those servers are enabled: mongodb
- Using images:
  - mcp/mongodb@sha256:44eed0f93b85db457e86d9a7de44aa032d6d9128aac05086194402adc4e2a9b7
- Pulling images [mcp/mongodb]
> Images pulled in 3.912ms
- Listing MCP tools...
  - Running server mcp/mongodb with [run --rm -i --init --security-opt no-new-privileges --cpus 1 --memory 2Gb --pull never --label docker-mcp=true --label docker-mcp-tool-type=mcp --label docker-mcp-name=mongodb --label docker-mcp-transport=stdio -e MDB_MCP_CONNECTION_STRING]
  > Can't start mongodb: initializing mcp/mongodb@sha256:44eed0f93b85db457e86d9a7de44aa032d6d9128aac05086194402adc4e2a9b7: Failed to connect to MongoDB instance using the connection string from the config:  TypeError: connectionString.startsWith is not a function
    at connectionStringHasValidScheme (/usr/local/lib/node_modules/mongodb-mcp-server/node_modules/mongodb-connection-string-url/lib/index.js:9:30)
    at new ConnectionString (/usr/local/lib/node_modules/mongodb-mcp-server/node_modules/mongodb-connection-string-url/lib/index.js:85:34)
    at setAppNameParamIfMissing (file:///usr/local/lib/node_modules/mongodb-mcp-server/dist/helpers/connectionOptions.js:3:33)
    at Session.connectToMongoDB (file:///usr/local/lib/node_modules/mongodb-mcp-server/dist/session.js:66:28)
    at Server.validateConfig (file:///usr/local/lib/node_modules/mongodb-mcp-server/dist/server.js:121:36)
    at Server.connect (file:///usr/local/lib/node_modules/mongodb-mcp-server/dist/server.js:49:20)
    at process.processTicksAndRejections (node:internal/process/task_queues:105:5)
    at async file:///usr/local/lib/node_modules/mongodb-mcp-server/dist/index.js:45:5

[himanshusinghs]

Hi @ImoutoChan! From the error it looks like the provided connection string is anything but a string, very likely getting resolved to some JS object. Can you check and confirm if the environment variable MDB_MCP_CONNECTION_STRING is being provided correctly or not, a string?