googleapis/mcp-toolbox · error

bucket cannot be empty for tool %q

Error message

bucket cannot be empty for tool %q

What it means

Thrown by cloudstorage-move-object Config.Initialize when the optional 'bucket' field is present but an empty string. Because move-object requires source and destination objects to be in the same bucket, a configured bucket must be a real bucket name; an empty one is rejected.

Source

Thrown at internal/tools/cloudstorage/cloudstoragemoveobject/cloudstoragemoveobject.go:75

	tools.ConfigBase `yaml:",inline"`
	Type             string                 `yaml:"type" validate:"required"`
	Source           string                 `yaml:"source" validate:"required"`
	Annotations      *tools.ToolAnnotations `yaml:"annotations,omitempty"`
	Bucket           *string                `yaml:"bucket,omitempty"`
}

var _ tools.ToolConfig = Config{}

func (cfg Config) ToolConfigType() string {
	return resourceType
}

func (cfg Config) Initialize(context.Context) (tools.Tool, error) {
	if cfg.Description == "" {
		return nil, fmt.Errorf("description is required for tool %q", cfg.Name)
	}
	if cfg.Bucket != nil && *cfg.Bucket == "" {
		return nil, fmt.Errorf("bucket cannot be empty for tool %q", cfg.Name)
	}

	sourceObjectParam := parameters.NewStringParameter(sourceObjectKey, "Full source object name (path) within the bucket, e.g. 'path/to/file.txt'.")
	destinationObjectParam := parameters.NewStringParameter(destinationObjectKey, "Full destination object name (path) within the same bucket, e.g. 'path/to/file.txt'.")
	allParameters := parameters.Parameters{}
	if cfg.Bucket == nil {
		allParameters = append(allParameters, parameters.NewStringParameter(bucketKey, "Name of the Cloud Storage bucket containing the object to move."))
	}
	allParameters = append(allParameters, sourceObjectParam, destinationObjectParam)

	return Tool{
		BaseTool: tools.NewBaseTool(
			cfg,
			tools.GetAnnotationsOrDefault(cfg.Annotations, tools.NewDestructiveAnnotations),
			tools.Manifest{Description: cfg.Description, Parameters: allParameters.Manifest(), AuthRequired: cfg.AuthRequired},
			allParameters,
		),
	}, nil

View on GitHub (pinned to 8cc6e09de2)

Solutions

1. Delete the 'bucket' key from the tool config to make it a per-call parameter instead
2. Provide a valid non-empty bucket name in the config
3. Fix the env var/secret feeding the value so it is no longer empty

Example fix

// before
  move-object:
    kind: cloudstorage-move-object
    source: my-gcs
    description: Move object
    bucket: ""
// after
  move-object:
    kind: cloudstorage-move-object
    source: my-gcs
    description: Move object
    bucket: my-bucket

if v, ok := cfg["bucket"]; ok {
    if s, isStr := v.(string); isStr && s == "" {
        return errors.New("bucket configured as empty string; unset it or supply a name")
    }
}

When it happens

Trigger: tools.yaml sets `bucket: ""` or an empty-expanded variable for a cloudstorage-move-object tool.

Common situations: Missing environment variable for bucket name; clearing the bucket value intending to unset the field; YAML quoting mistakes.

Understand the failure class

Background: "is required", "must be set", "missing required field": configuration validation errors across open-source libraries — this error's family across 36 libraries.

Related errors

• description is required for tool %q
• bucket cannot be empty for tool %q
• description is required for tool %q
• description is required for tool %q
• bucket cannot be empty for tool %q

AI-assisted analysis of googleapis/mcp-toolbox@8cc6e09de2 (2026-09-05). Data as JSON: /api/errors/e0464454e39c0df7. Report an issue: GitHub.