NousResearch/hermes-agent · warning · Error

Command required

Error message

Command required

What it means

For stdio-transport MCP servers (the non-http branch of buildMcpServerCreate), the command to launch is required; args and env are optional. A trimmed-empty command throws before the payload is built. The command is the executable the gateway will spawn for this MCP server.

Source

Thrown at web/src/lib/mcp-server-create.ts:70

  if (!name) throw new Error("Name required");

  if (draft.transport === "http") {
    const url = draft.url.trim();
    if (!url) throw new Error("URL required");
    if (draft.httpAuth === "header" && !draft.bearerToken.trim()) {
      throw new Error("Bearer token required");
    }

    const server: McpServerCreate = { name, url };
    if (draft.httpAuth !== "none") server.auth = draft.httpAuth;
    if (draft.httpAuth === "header") {
      server.bearer_token = draft.bearerToken;
    }
    return server;
  }

  const command = draft.command.trim();
  if (!command) throw new Error("Command required");

  const server: McpServerCreate = { name, command };
  const args = parseArgs(draft.args);
  if (args.length) server.args = args;
  const env = parseEnv(draft.env);
  if (Object.keys(env).length) server.env = env;
  return server;
}

View on GitHub (pinned to c896c09c42)

Solutions

1. Enter the launch command (e.g. npx, uvx, or a binary path) in the command field.
2. If configuring a remote server, switch the transport to http and fill the URL instead.
3. Validate command.trim() client-side before calling buildMcpServerCreate on the stdio branch.

if (draft.transport !== 'http' && !draft.command.trim()) {
  setFieldError('command', 'Command is required for stdio servers')
  return
}

function hasStdioCommand(d: McpServerDraft): boolean {
  return d.transport !== 'http' || d.command.trim().length > 0
}

try {
  const payload = buildMcpServerCreate(draft)
} catch (err) {
  if (String(err) === 'Command required') { focusField('command'); return }
  throw err
}

When it happens

Trigger: Leaving the command field blank on the stdio branch; a draft with transport undefined/null falling through to the stdio path while only URL was filled; whitespace-only command.

Common situations: Transport selector defaulting to stdio while the user filled the HTTP URL field; form fields not cleared/swapped when toggling transport; scripts creating servers from templates missing `command`.

Related errors

• Name required
• URL required
• Bearer token required
• Preview mode — launching is disabled.
• no install root

AI-assisted analysis of NousResearch/hermes-agent@c896c09c42 (2026-08-14). Data as JSON: /api/errors/b22e1f30d83c0fce. Report an issue: GitHub.