googleapis/mcp-toolbox · error

toolbox failed to initialize: %w

Error message

toolbox failed to initialize: %w

What it means

server.NewServer builds the toolbox server from the resolved config (loading tools files, initializing sources, validating auth services). Any failure there is wrapped with 'toolbox failed to initialize' and logged, so the exact cause is in the wrapped %w error on the next line of the log.

Source

Thrown at cmd/root.go:467

		if opts.Cfg.EnableAPI {
			errMsg := fmt.Errorf("MCP Auth cannot be enabled together with the legacy HTTP API (--enable-api)")
			opts.Logger.ErrorContext(ctx, errMsg.Error())
			return errMsg
		}
		if opts.Cfg.ToolboxUrl == "" {
			opts.Cfg.ToolboxUrl = os.Getenv("TOOLBOX_URL")
		}
		if opts.Cfg.ToolboxUrl == "" {
			errMsg := fmt.Errorf("MCP Auth is enabled but Toolbox URL is missing. Please provide it via --toolbox-url flag or TOOLBOX_URL environment variable")
			opts.Logger.ErrorContext(ctx, errMsg.Error())
			return errMsg
		}
	}

	// 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)
	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. Read the wrapped '%w' cause line in the log for the underlying error
2. Validate tools.yaml syntax and source credentials
3. Run with debug logging to see which source/tool/auth failed
4. Test database connectivity separately (e.g. psql/mysql client)

Example fix

// before
tools.yaml: sources:
  my-pg:
    kind: postgres
    uri: ${DB_URI}  # env var unset -> empty uri
// after
export DB_URI=postgres://user:pass@host:5432/db

# validate config before launch
go run . --tools-file tools.yaml --dry-run 2>&1 || echo 'toolbox config invalid'
# and check env interpolation
env | grep -E 'DB_|API_KEY' >/dev/null || echo 'missing source env vars'

// wrapper around launching toolbox
out, err := exec.CommandContext(ctx, "./toolbox", args...).CombinedOutput()
if err != nil && strings.Contains(string(out), "toolbox failed to initialize") {
    // parse the wrapped '%w' cause line and fix tools.yaml/sources
    log.Fatalf("toolbox init failed: %s", out)
}

When it happens

Trigger: Invalid tools.yaml / prebuilt config, a source failing to initialize (bad credentials, unreachable database), or an invalid auth service config passed into server.NewServer.

Common situations: Malformed YAML, wrong connection strings/secrets, unsupported tool kind, invalid auth configuration, missing required fields in a source config.

Related errors

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

AI-assisted analysis of googleapis/mcp-toolbox@8cc6e09de2 (2026-09-05). Data as JSON: /api/errors/c312baac869b2d02. Report an issue: GitHub.