googleapis/mcp-toolbox · error

description is required for tool %q

Error message

description is required for tool %q

What it means

Looker tools require a human-readable description at tool-initialization time. Config.Initialize returns this error when the Config's Description field is empty, because a tool cannot be registered with the MCP server without a description for the LLM.

Source

Thrown at internal/tools/looker/lookeradddashboardelement/lookeradddashboardelement.go:72

}

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)
	}

	params := lookercommon.GetQueryParameters()

	dashIdParameter := parameters.NewStringParameter("dashboard_id", "The id of the dashboard where this tile will exist")
	params = append(params, dashIdParameter)
	titleParameter := parameters.NewStringParameter("title", "The title of the Dashboard Element", parameters.WithStringDefault(""))
	params = append(params, titleParameter)
	vizParameter := parameters.NewMapParameter(
		"vis_config",
		"The visualization config for the query",
		"",
		parameters.WithMapDefault(map[string]any{}),
	)

	params = append(params, vizParameter)
	dashFilters := parameters.NewArrayParameter(
		"dashboard_filters",

View on GitHub (pinned to 8cc6e09de2)

Solutions

1. Add a non-empty description field to the tool's YAML config, e.g. description: Adds an element to a Looker dashboard
2. Check for misspelled/indented YAML keys so the value actually lands in cfg.Description
3. If templated, ensure the template renders a non-empty string

Example fix

// before
kind: looker-add-dashboard-element
name: add_tile
source: looker-source
// after
kind: looker-add-dashboard-element
name: add_tile
source: looker-source
description: Adds a tile element to an existing Looker dashboard

if cfg.Description == "" {
    return errors.New("description is required for looker tools")
}

tool, err := cfg.Initialize(ctx)
if err != nil && strings.Contains(err.Error(), "description is required") {
    // add description to the tool entry in tools.yaml and reload
    return err
}

When it happens

Trigger: A tools.yaml entry for kind: looker-add-dashboard-element omits the description field or sets it to "" and the server starts, invoking Initialize.

Common situations: Minimal example configs copy-pasted without the description; YAML key misspelled (desc:, descrption:) leaving the field zero-valued; description removed during config cleanup; empty string after templating.

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

• description is required for tool %q
• description is required for tool %q
• description is required for tool %q
• description is required for tool %q
• invalid source for %q tool: source %q is not a compatible ty

AI-assisted analysis of googleapis/mcp-toolbox@8cc6e09de2 (2026-09-05). Data as JSON: /api/errors/b4efca0a73a05195. Report an issue: GitHub.