Paste your VS Code mcp.json, hit Validate. Headline gotcha: this file uses a top-level servers key — mcpServers here means you pasted a portable .mcp.json by mistake. Runs 100% in your browser — nothing is uploaded.
JSON syntax — the file must parse. Trailing commas and comments are the usual culprits.Top-level "servers" (not "mcpServers") — the VS Code workspace format uses servers. A top-level mcpServers key fails with the gotcha note: that shape belongs in a portable .mcp.json at the project root instead.At least one server — an empty servers object means nothing will start.type enum — when type is present it must be one of stdio, http or sse. A missing type is allowed (command entries default to stdio).stdio fields — servers with command (or type: stdio) need a non-empty command string; args must be an array of strings when present.Remote fields — servers with url (or type: http/sse) need a url string; a remote-typed server with no url fails.env shape — env must be an object of string values when present. Never hardcode API keys — use input variables or env files.secret values pasted in env (heuristic warning) and insecure http:// URLs on non-local endpoints..vscode/mcp.json with top-level servers, portable .mcp.json with mcpServers, stdio/http/sse types, no-hardcoded-secrets guidance). Full field reference lives in the VS Code MCP configuration reference.