googleapis/mcp-toolbox · error

description is required for tool %q

Error message

description is required for tool %q

What it means

This error is thrown by the clickhouseexecutesql tool's Config.Initialize when the tool config's Description is empty. A non-empty description is required for the MCP tool manifest, so the tool fails to initialize and is excluded from the server.

Source

Thrown at internal/tools/clickhouse/clickhouseexecutesql/clickhouseexecutesql.go:64

	RunSQL(context.Context, string, parameters.ParamValues) (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 executeSQLType
}

func (cfg Config) Initialize(context.Context) (tools.Tool, error) {
	if cfg.Description == "" {
		return nil, fmt.Errorf("description is required for tool %q", cfg.Name)
	}

	sqlParameter := parameters.NewStringParameter("sql", "The SQL statement to execute.")
	params := parameters.Parameters{sqlParameter}

	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
}

var _ tools.Tool = Tool{}

type Tool struct {

View on GitHub (pinned to 8cc6e09de2)

Solutions

1. Add a non-empty description field to the clickhouse-execute-sql tool in tools.yaml
2. Ensure any env/template substitution for description produces a non-empty string
3. Correct YAML nesting so description belongs to the tool
4. Restart the server and verify the tool registers

Example fix

// before (tools.yaml)
tools:
  clickhouse-sql:
    kind: clickhouse-execute-sql
    source: my-clickhouse
// after
tools:
  clickhouse-sql:
    kind: clickhouse-execute-sql
    source: my-clickhouse
    description: Executes a SQL statement against ClickHouse.

// Validate before constructing the tool
cfg := clickhouseexecutesql.Config{Name: "clickhouse-sql", Source: "my-clickhouse"}
if strings.TrimSpace(cfg.Description) == "" {
    return fmt.Errorf("tool %q requires a non-empty description", cfg.Name)
}
// Or lint the YAML: tools["clickhouse-sql"].description must be present and non-empty

func hasDescription(name, desc string) bool {
    return strings.TrimSpace(desc) != ""
}

When it happens

Trigger: Calling Initialize on a clickhouseexecutesql Config with Description == "" — e.g. a tools.yaml entry of kind clickhouse-execute-sql missing the description key or with an empty value after expansion.

Common situations: Hand-written tools.yaml without description; templated description variables resolving to empty; YAML indentation placing description outside the tool block; copied snippets omitting the field.

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
• description is required for tool %q

AI-assisted analysis of googleapis/mcp-toolbox@8cc6e09de2 (2026-09-05). Data as JSON: /api/errors/5c784190faab3377. Report an issue: GitHub.