googleapis/mcp-toolbox · error

description is required for tool %q

Error message

description is required for tool %q

What it means

cloud-storage-deletebucket's Config.Initialize enforces a non-empty tool description before constructing the tool. The description is required because it is shown to LLM clients; an empty description fails config loading with this error.

Source

Thrown at internal/tools/cloudstorage/cloudstoragedeletebucket/cloudstoragedeletebucket.go:67

	DeleteBucket(ctx context.Context, bucket string) (map[string]any, error)
}

type Config struct {
	tools.ConfigBase `yaml:",inline"`
	Type             string                 `yaml:"type" validate:"required"`
	Source           string                 `yaml:"source" validate:"required"`
	Annotations      *tools.ToolAnnotations `yaml:"annotations,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)
	}

	bucketParam := parameters.NewStringParameter(bucketKey, "Name of the empty Cloud Storage bucket to delete.")
	allParameters := parameters.Parameters{bucketParam}

	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
}

var _ tools.Tool = Tool{}

type Tool struct {

View on GitHub (pinned to 8cc6e09de2)

Solutions

1. Add a non-empty `description` to the delete_bucket tool config
2. Run config validation/linting in CI to catch missing fields pre-deploy
3. Check YAML nesting so description sits under the tool, not a sibling

Example fix

// before
- name: delete_bucket
  source: my-gcs
// after
- name: delete_bucket
  source: my-gcs
  description: Deletes an empty Cloud Storage bucket by name

func validateDeleteBucketTool(cfg map[string]any) error {
    d, _ := cfg["description"].(string)
    if strings.TrimSpace(d) == "" {
        return fmt.Errorf("tool %v: description is required", cfg["name"])
    }
    return nil
}

func hasDescription(cfg Config) bool { return cfg.Description != "" }

tool, err := cfg.Initialize(ctx)
if err != nil && strings.Contains(err.Error(), "description is required") {
    return fmt.Errorf("add description to delete_bucket in tools.yaml: %w", err)
}

When it happens

Trigger: A delete_bucket tool definition in tools.yaml missing the `description` field; Initialize runs at server startup and returns the error.

Common situations: Hand-written YAML missing description; templated configs where the description field evaluated to an empty string; indentation errors placing description under the wrong node.

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
• source_bucket cannot be empty for tool %q
• destination_bucket cannot be empty for tool %q
• description is required for tool %q
• doc %d: unexpected non-string key in input: %v

AI-assisted analysis of googleapis/mcp-toolbox@8cc6e09de2 (2026-09-05). Data as JSON: /api/errors/02f095df1b81725e. Report an issue: GitHub.