googleapis/mcp-toolbox · critical

toolbox failed to initialize: %w

Error message

toolbox failed to initialize: %w

What it means

runServe calls server.NewServer(ctx, opts.Cfg) to assemble the toolbox server (sources, tools, auth, manifests). Any initialization failure — invalid source config, tool initialization error, duplicate tool names, etc. — is wrapped with this message and the serve command exits.

Source

Thrown at cmd/internal/serve/command.go:77

			opts.Logger.DebugContext(sCtx, "Received SIGINT signal to shutdown.")
		case syscall.SIGTERM:
			opts.Logger.DebugContext(sCtx, "Received SIGTERM signal to shutdown.")
		}
		cancel()
	}(ctx)

	ctx, shutdown, err := opts.Setup(ctx)
	if err != nil {
		return err
	}
	defer func() {
		_ = shutdown(ctx)
	}()

	// start server
	s, err := server.NewServer(ctx, opts.Cfg)
	if err != nil {
		errMsg := fmt.Errorf("toolbox failed to initialize: %w", err)
		opts.Logger.ErrorContext(ctx, errMsg.Error())
		return errMsg
	}

	useTLS := opts.Cfg.CertFile != "" || opts.Cfg.KeyFile != ""
	protocol := "http"
	if useTLS {
		protocol = "https"
	}

	// run server in background
	srvErr := make(chan error, 1)
	if opts.Cfg.Stdio {
		go func() {
			defer close(srvErr)
			err = s.ServeStdio(ctx, opts.IOStreams.In, opts.IOStreams.Out)
			if err != nil {
				srvErr <- err

View on GitHub (pinned to 8cc6e09de2)

Solutions

1. Inspect the wrapped root cause — it names the specific source/tool that failed
2. Verify all source connection strings, credentials, and env vars resolve correctly
3. Test database connectivity manually (psql/mysql client, etc.) before starting toolbox
4. Validate the tools config YAML structure against the documented schema

Example fix

// before
sources:
  my-pg:
    kind: postgres
    host: db.internal  # unreachable
    port: 5432
    database: mydb
    user: app
    password: ${DB_PASS}
// after
sources:
  my-pg:
    kind: postgres
    host: localhost
    port: 5432
    database: mydb
    user: app
    password: ${DB_PASS}

// verify connectivity before starting toolbox
nc -zv $DB_HOST $DB_PORT || echo "database unreachable"
# and validate the config file parses:
./toolbox --tools-file tools.yaml --dry-run 2>/dev/null || true

s, err := server.NewServer(ctx, cfg)
if err != nil {
    return fmt.Errorf("toolbox failed to initialize: %w", err)
}

When it happens

Trigger: server.NewServer fails: a source fails to connect/authenticate during Initialize, a tool's Initialize errors, or config validation fails.

Common situations: Bad database connection string, missing DB password env var, unreachable database host, invalid YAML tool definitions, or unsupported tool type in the config file.

Related errors

• toolbox failed to initialize: %w
• unable to initialize reloaded configs: %w
• unable to initialize configs: %w
• unable to create pool: %w
• unable to create admin client: %w

AI-assisted analysis of googleapis/mcp-toolbox@8cc6e09de2 (2026-09-05). Data as JSON: /api/errors/5b5f1f7ac52def3e. Report an issue: GitHub.