googleapis/mcp-toolbox · error

description is required for tool %q

Error message

description is required for tool %q

What it means

cloudgda.Config.Initialize validates that a non-empty description was provided before constructing the tool. In this codebase the description is user-supplied in tools.yaml (the tool does not ship a default), so an empty description makes the tool un-instantiable. The error names the offending tool via cfg.Name.

Source

Thrown at internal/tools/cloudgda/cloudgda.go:130

	tools.ConfigBase  `yaml:",inline"`
	Type              string                 `yaml:"type" validate:"required"`
	Source            string                 `yaml:"source" validate:"required"`
	Location          string                 `yaml:"location" validate:"required"`
	Context           *QueryDataContext      `yaml:"context" validate:"required"`
	GenerationOptions *GenerationOptions     `yaml:"generationOptions,omitempty"`
	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)
	}

	// Define the parameters for the Gemini Data Analytics Query API
	// The query is the only input parameter.
	allParameters := parameters.Parameters{
		parameters.NewStringParameter("query", "A natural language formulation of a database query.", parameters.WithStringRequired(true)),
	}
	// The input and outputs are for tool guidance, usage guidance is for multi-turn interaction.
	guidance := Guidance
	cfg.Description += "\n\n" + guidance

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

View on GitHub (pinned to 8cc6e09de2)

Solutions

1. Add a non-empty description field to the cloudgda tool's yaml block in tools.yaml
2. Verify the key is spelled exactly 'description' and is not an empty string
3. Check that YAML anchors/overrides used to build the config do not blank the field

Example fix

// before
tools:
  my-gda-tool:
    kind: cloud-gemini-data-analytics-query
    source: my-gda-source
// after
tools:
  my-gda-tool:
    kind: cloud-gemini-data-analytics-query
    source: my-gda-source
    description: "Run natural language queries against BigQuery using Gemini Data Analytics"

// pre-check your tools.yaml
func toolHasDescription(name string, cfg map[string]map[string]any) error {
	t := cfg["tools"][name].(map[string]any)
	d, _ := t["description"].(string)
	if d == "" { return fmt.Errorf("description missing for %s", name) }
	return nil
}

When it happens

Trigger: A cloudgda tool definition in tools.yaml where the description field is missing, set to an empty string, or set to "" via an empty YAML anchor.

Common situations: Writing a minimal tools.yaml and forgetting description; a templated config where description resolves to empty; YAML key misspelled (descripton) so the field stays zero-valued.

Understand the failure class

Background: "missing required argument" and "the following required arguments were not provided": what required-argument errors mean and how to fix them — this error's family across 20 libraries.

Related errors

• doc %d: unexpected non-string key in input: %v
• doc %d: invalid config format at key %q: %w
• doc %d: invalid config format at key %q: expected nested for
• %s missing 'kind' field or it is not a string
• missing 'kind' field or it is not a string: %v

AI-assisted analysis of googleapis/mcp-toolbox@8cc6e09de2 (2026-09-05). Data as JSON: /api/errors/67e2ee27a06bb52e. Report an issue: GitHub.