MCP server " ": missing required "url" for transport

Error message

MCP server "${name}": missing required "url" for ${server.type || "sse"} transport

What it means

During hypervisor boot, an http-classified MCP server entry (has url or type sse/streamable/http) must contain a non-empty "url" property. #validateServerDefinitionByType throws this templated message when server.url is missing, interpolating the declared transport (defaulting to "sse").

Solutions

Add the full "url" (including scheme) to the http/sse/streamable server entry
If the server is actually a local process, remove "type" and use { "command": ..., "args": [...] } instead
Check for key typos — the hypervisor looks for exactly "url"
Re-boot MCP servers after fixing the JSON

Example fix

// before
{ "my-server": { "type": "streamable" } }

// after
{ "my-server": { "type": "streamable", "url": "https://example.com/mcp" } }

Defensive patterns

Strategy: validation

Validate before calling

function requireUrl(server) {
  if (server.type !== 'stdio' && !server.url)
    throw new Error('http/sse/streamable MCP servers require a "url" field');
}

Type guard

function hasTransportField(server) {
  return typeof server.url === 'string' || typeof server.command === 'string';
}

Try / catch

try {
  await addMcpServer(entry);
} catch (err) {
  if (err.message.includes('missing required "url"')) {
    // prompt for the endpoint URL
  }
  throw err;
}

Prevention

Require the url field in the MCP server form before submit
Validate JSON shape (url or command present) immediately after any manual edit
Document that only the exact key 'url' is recognized

When it happens

Trigger: mcp_servers.json entry classified as http (e.g. { "type": "sse" } with no url, or { "url": "" }) — #parseServerType returned "http" via the type field but the required url is absent or empty.

Common situations: Entry written with only a command but a type of sse; url key typo'd as "endpoint", "uri", or "base_url"; empty-string url left after an incomplete edit; copy-paste from a config that used a different key name.

Related errors

AI-assisted analysis of Mintplex-Labs/anything-llm@3aec848f28 (2026-08-18). Data as JSON: /api/errors/5c2f3ae2c222fe57. Report an issue: GitHub.

Appendix: source

Thrown at server/utils/MCP/hypervisor/index.js:376

   * - Will throw an error if the server definition is invalid
   * @param {string} name - The name of the MCP server
   * @param {Object} server - The server definition
   * @param {MCPServerTypes} type - The server type
   * @returns {void}
   */
  #validateServerDefinitionByType(name, server, type) {
    if (type === "http") {
      // "type" is optional for http servers - when omitted, SSE is assumed
      // (see createHttpTransport). An explicit unknown value is a config error.
      if (
        server.type !== undefined &&
        !["sse", "streamable", "http"].includes(server.type)
      ) {
        throw new Error("MCP server type must have sse or streamable value.");
      }

      if (!server.url) {
        throw new Error(
          `MCP server "${name}": missing required "url" for ${server.type || "sse"} transport`
        );
      }

      try {
        new URL(server.url);
      } catch {
        throw new Error(`MCP server "${name}": invalid URL "${server.url}"`);
      }
      return;
    }

    if (type === "stdio") {
      if (
        Object.prototype.hasOwnProperty.call(server, "args") &&
        !Array.isArray(server.args)
      )
        throw new Error("MCP server args must be an array");

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