nanocoai/nanoclaw · error · Error

type "stdio" requires command

Error message

type "stdio" requires command

What it means

Thrown by parseMcpServerConfig when an MCP server entry declares type "stdio" but omits the required `command` field. A stdio MCP server is launched by executing a local binary, so the command is mandatory; the config is rejected before it can reach the container spec.

Source

Thrown at src/container-config.ts:138

/**
 * Parse one CLI or approval payload into the persisted MCP config shape.
 * Duplicated in container/agent-runner/src/mcp-tools/self-mod.ts
 * (parseMcpServerInput) — no shared modules across the host/container
 * boundary; keep the two in sync.
 */
export function parseMcpServerConfig(input: Record<string, unknown>): McpServerConfig {
  const command = typeof input.command === 'string' && input.command.trim() ? input.command : undefined;
  const url = typeof input.url === 'string' && input.url.trim() ? input.url.trim() : undefined;

  // A declared transport is honored; absence keeps the legacy CLI inference
  // (url → http, command → stdio). "streamable-http" is the Agent Plugins
  // spelling of the internal "http".
  const type = input.type === 'streamable-http' ? 'http' : input.type;
  if (type === 'sse') throw new Error('unsupported transport "sse"');
  if (type !== undefined && type !== 'stdio' && type !== 'http') {
    throw new Error('type must be "stdio", "http", or "streamable-http"');
  }
  if (type === 'stdio' && !command) throw new Error('type "stdio" requires command');
  if (type === 'http' && !url) throw new Error('type "http" requires url');

  const instructions = input.instructions;
  if (instructions !== undefined && typeof instructions !== 'string') {
    throw new Error('MCP instructions must be a string');
  }

  if (url !== undefined) {
    if (command !== undefined) throw new Error('Provide exactly one of command or url');
    if (input.args !== undefined || input.env !== undefined || input.cwd !== undefined) {
      throw new Error('args, env, and cwd are only valid with command');
    }
    let parsed: URL;
    try {
      parsed = new URL(url);
    } catch (err) {
      throw new Error('url must be a valid HTTP(S) URL', { cause: err });
    }

View on GitHub (pinned to 294ef2aee8)

Solutions

1. Add a `command` field naming the executable, e.g. {"type":"stdio","command":"npx","args":["-y","some-mcp-server"]}
2. If you meant a remote server, use type "http"/"streamable-http" with a url instead
3. Verify the JSON you passed with ncl groups config get to see the parsed entry

Example fix

// before
{"type":"stdio","args":["-y","server"]}
// after
{"type":"stdio","command":"npx","args":["-y","server"]}

const srv = input; // before parseMcpServerConfig
if (srv.type === 'stdio' && !srv.command) throw new UserError('stdio MCP entry needs command');

function isValidStdioEntry(e: any): e is {type:'stdio'; command:string} {
  return e?.type === 'stdio' && typeof e.command === 'string' && e.command.length > 0;
}

catch (err) { if (err instanceof Error && err.message.includes('requires command')) showFieldError('command', err); else throw err; }

When it happens

Trigger: Calling ncl groups config add-mcp-server (or the add_mcp_server self-mod MCP tool) with --type stdio and only a url, or with no command/url at all; also any programmatic call to parseMcpServerConfig with {type:'stdio'} lacking command.

Common situations: Copy-pasting an HTTP server config and changing type to stdio without replacing url with command; assuming a default command exists; omitting command because the server 'name' looks executable.

Related errors

• type "http" requires url
• server name must be 1-64 characters of letters, digits, "_"
• unsupported transport "sse"
• type must be "stdio", "http", or "streamable-http"
• MCP instructions must be a string

AI-assisted analysis of nanocoai/nanoclaw@294ef2aee8 (2026-08-28). Data as JSON: /api/errors/49059761e4353fa8. Report an issue: GitHub.