googleapis/mcp-toolbox · error

unable to merge config files: %w

Error message

unable to merge config files: %w

What it means

When more than one config was loaded, mergeConfigs combines them; any error from the merge (duplicate names, multiple mcpEnabled authServices) is wrapped as 'unable to merge config files' with the underlying reason.

Source

Thrown at cmd/internal/config.go:527

		buf, err := os.ReadFile(filePath)
		if err != nil {
			return Config{}, fmt.Errorf("unable to read config file at %q: %w", filePath, err)
		}

		config, err := p.ParseConfig(ctx, buf)
		if err != nil {
			return Config{}, fmt.Errorf("unable to parse config file at %q: %w", filePath, err)
		}

		configs = append(configs, config)
	}
	if len(configs) == 0 {
		return Config{}, fmt.Errorf("no YAML files found")
	}
	if len(configs) > 1 {
		mergedFile, err := mergeConfigs(configs...)
		if err != nil {
			return Config{}, fmt.Errorf("unable to merge config files: %w", err)
		}
		return mergedFile, nil
	}
	return configs[0], nil
}

// GetPathsFromConfigFolder loads all YAML files from a directory and merges them
func GetPathsFromConfigFolder(ctx context.Context, folderPath string) ([]string, error) {
	// Check if directory exists
	info, err := os.Stat(folderPath)
	if err != nil {
		return nil, fmt.Errorf("unable to access config folder at %q: %w", folderPath, err)
	}
	if !info.IsDir() {
		return nil, fmt.Errorf("path %q is not a directory", folderPath)
	}

	// Find all YAML files in the directory

View on GitHub (pinned to 8cc6e09de2)

Solutions

1. Read the wrapped cause to find the conflict (usually duplicate names)
2. Rename duplicates so each source/tool/authService/prompt/group is unique
3. Deduplicate the list of config files being passed

Example fix

// before
toolbox --config-file a.yaml --config-file a.yaml
// after
toolbox --config-file a.yaml --config-file b.yaml

if hasDuplicates(filePaths) {
  return fmt.Errorf("duplicate config files passed: %v", filePaths)
}
// plus pre-check for duplicate resource names as in error 22

cfg, err := parser.LoadAndMergeConfigs(ctx, files)
if err != nil {
  if strings.Contains(err.Error(), "unable to merge config files") {
    var mergeErr error
    if errors.Unwrap(err) != nil { mergeErr = errors.Unwrap(err) }
    // inspect mergeErr for the specific conflict
  }
  return err
}

When it happens

Trigger: LoadAndMergeConfigs with len(configs) > 1 where mergeConfigs returns an error — typically duplicate resource names across files or conflicting MCP auth servers.

Common situations: Combining prebuilt configs with custom files that share tool/source names; passing overlapping config files twice.

Related errors

• resource conflicts detected: - %s Please ensure each sour
• multiple authServices with mcpEnabled=true detected: %s. Onl

AI-assisted analysis of googleapis/mcp-toolbox@8cc6e09de2 (2026-09-05). Data as JSON: /api/errors/217d3b18615ee687. Report an issue: GitHub.