What causes "description is required for tool %q" in googleapis/mcp-toolbox?

Add a non-empty `description` to the looker-get-dashboards tool entry in tools.yaml.

description is required for tool %q

Error message

description is required for tool %q

What it means

During looker-get-dashboards Config.Initialize, a guard rejects configurations whose `description` field is empty. The description becomes the tool's manifest description that MCP/LLM clients rely on, so an empty one makes the tool config invalid and initialization aborts.

Source

Thrown at internal/tools/looker/lookergetdashboards/lookergetdashboards.go:71

}

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"`
}

// 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)
	}

	titleParameter := parameters.NewStringParameter("title", "The title of the dashboard.", parameters.WithStringDefault(""))
	descParameter := parameters.NewStringParameter("desc", "The description of the dashboard.", parameters.WithStringDefault(""))
	limitParameter := parameters.NewIntParameter("limit", "The number of dashboards to fetch. Default 100", parameters.WithIntDefault(100))
	offsetParameter := parameters.NewIntParameter("offset", "The number of dashboards to skip before fetching. Default 0", parameters.WithIntDefault(0))
	params := parameters.Parameters{
		titleParameter,
		descParameter,
		limitParameter,
		offsetParameter,
	}

	// finish tool setup
	return Tool{
		BaseTool: tools.NewBaseTool(
			cfg,
			tools.GetAnnotationsOrDefault(cfg.Annotations, tools.NewReadOnlyAnnotations),

View on GitHub (pinned to 8cc6e09de2)

Solutions

Add a non-empty `description` to the looker-get-dashboards tool entry in tools.yaml.
Check YAML indentation so `description` is a child of the tool, not a sibling.
When constructing configs programmatically, set cfg.Description before calling Initialize.
Run `toolbox validate` in CI to catch missing descriptions before serving.

Example fix

// before (tools.yaml)
  get-dashboards:
    kind: looker-get-dashboards
    source: my-looker
// after
  get-dashboards:
    kind: looker-get-dashboards
    source: my-looker
    description: Searches and lists Looker dashboards by title or description.

Defensive patterns

Strategy: validation

Validate before calling

if strings.TrimSpace(cfg.Description) == "" {
    return errors.New("tool 'get-dashboards': description is required")
}

Try / catch

tool, err := cfg.Initialize(ctx)
if err != nil {
    log.Fatalf("invalid looker-get-dashboards config: %v", err)
}

Prevention

Give every tool entry a description in tools.yaml.
Run `toolbox validate` in CI to catch missing descriptions.
Lint YAML configs for required keys (name, kind, source, description).
Avoid generators that omit optional description fields.

When it happens

Trigger: Loading a tools.yaml with a tool of kind looker-get-dashboards that has no `description` field, or building the Config in Go with Name set but Description empty and calling Initialize.

Common situations: Hand-edited YAML omitting the description; description indented under the wrong key; config generators/templating producing an empty string.

Related errors

AI-assisted analysis of googleapis/mcp-toolbox@8cc6e09de2 (2026-09-05). Data as JSON: /api/errors/500df0d2c53fa540. Report an issue: GitHub.