googleapis/mcp-toolbox · error

bucket cannot be empty for tool %q

Error message

bucket cannot be empty for tool %q

What it means

cloudstorage-get-object-metadata's Initialize rejects a bucket field that is a non-nil pointer to an empty string. Provide a real bucket name or omit the field entirely so bucket becomes a required parameter on the tool.

Source

Thrown at internal/tools/cloudstorage/cloudstoragegetobjectmetadata/cloudstoragegetobjectmetadata.go:76

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

// validate interface
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)
	}

	objectParam := parameters.NewStringParameter(objectKey, "Full object name (path) within the 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."))
	}
	allParameters = append(allParameters, objectParam)

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

View on GitHub (pinned to 8cc6e09de2)

Solutions

1. Set `bucket: <real-bucket-name>` in the config.
2. Omit the `bucket` key to make it a per-invocation parameter.
3. Add config linting to reject empty string values for resource-name fields.

Example fix

# before
bucket: ""
# after
bucket: my-gcs-bucket

if cfg.Bucket != nil && strings.TrimSpace(*cfg.Bucket) == "" {
    return errors.New("bucket cannot be empty; set a name or omit the field")
}

func bucketSet(cfg Config) bool { return cfg.Bucket != nil && *cfg.Bucket != "" }

When it happens

Trigger: cfg.Bucket != nil and *cfg.Bucket == "" during Initialize — e.g. `bucket: ""` in YAML or tools.Ptr("") in Go.

Common situations: Empty string from env-var interpolation; YAML key left with no value; build-time templating leaving placeholders unresolved.

Related errors

• bucket cannot be empty for tool %q
• bucket cannot be empty for tool %q
• invalid source for %q tool: source %q is not a compatible ty
• description is required for tool %q
• description is required for tool %q

AI-assisted analysis of googleapis/mcp-toolbox@8cc6e09de2 (2026-09-05). Data as JSON: /api/errors/4674c5a6906080a2. Report an issue: GitHub.