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

Add a non-empty description field to the bigquery-execute-sql tool definition in your config.

description is required for tool %q

Error message

description is required for tool %q

What it means

The bigquery-execute-sql tool's Config.Initialize returns this error when the tool's Description field is empty. Descriptions are required because they are surfaced to the LLM as the tool's prompt-level documentation. The check runs at configuration/initialization time, before any request is served.

Source

Thrown at internal/tools/bigquery/bigqueryexecutesql/bigqueryexecutesql.go:80

}

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, err := buildParams("", nil)
	if err != nil {
		return nil, err
	}
	return Tool{
		BaseTool: tools.NewBaseTool(
			cfg,
			tools.GetAnnotationsOrDefault(cfg.Annotations, tools.NewDestructiveAnnotations),
			tools.Manifest{Description: cfg.Description, Parameters: params.Manifest(), AuthRequired: cfg.AuthRequired},
			params,
		),
	}, nil
}

// validate interface
var _ tools.Tool = Tool{}

View on GitHub (pinned to 8cc6e09de2)

Solutions

Add a non-empty description field to the bigquery-execute-sql tool definition in your config.
Verify YAML indentation so description is a sibling of name/kind, not nested or swallowed.
If building Config in Go, set cfg.Description before calling Initialize.

Example fix

// before (tools.yaml)
tools:
  execute-sql:
    kind: bigquery-execute-sql
    source: my-bigquery-source
// after
tools:
  execute-sql:
    kind: bigquery-execute-sql
    source: my-bigquery-source
    description: Runs BigQuery SQL statements against the configured datasets.

Defensive patterns

Strategy: validation

Validate before calling

if cfg.Description == "" {
    return fmt.Errorf("tool %q: description is required", cfg.Name)
}
if err := cfg.Initialize(context.Background()); err != nil { /* handle before serving */ }

Try / catch

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

Prevention

Never leave description empty in tool definitions; treat it as a required field in your config linter.
Run server startup config validation in CI to catch missing fields early.
Watch YAML indentation when hand-editing tools.yaml.
Use schema validation (yaml lint against the toolbox schema) before deploy.

When it happens

Trigger: Declaring a bigquery-execute-sql tool in the YAML config (or constructing Config programmatically) without setting the description field, then calling Initialize.

Common situations: Hand-written tools.yaml with a missing or empty description key; YAML indentation mistakes that drop the description field; programmatic tool construction where Description was left at its zero value.

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

AI-assisted analysis of googleapis/mcp-toolbox@8cc6e09de2 (2026-09-05). Data as JSON: /api/errors/cbf34a60ec4bc4f8. Report an issue: GitHub.