googleapis/mcp-toolbox · error

description is required for tool %q

Error message

description is required for tool %q

What it means

The redis tool's Initialize returns this error when the tool's `description` field is empty in tools.yaml. Every tool requires a human-readable description because it is surfaced to the LLM as the tool's manifest description, letting the model decide when to invoke the tool.

Source

Thrown at internal/tools/redis/redis.go:68

type Config struct {
	tools.ConfigBase `yaml:",inline"`
	Type             string                 `yaml:"type" validate:"required"`
	Source           string                 `yaml:"source" validate:"required"`
	Commands         [][]string             `yaml:"commands" validate:"required"`
	Parameters       parameters.Parameters  `yaml:"parameters"`
	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)
	}

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

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

type Tool struct {
	tools.BaseTool[Config]
}

View on GitHub (pinned to 8cc6e09de2)

Solutions

1. Add a non-empty `description:` field to the redis tool entry in tools.yaml
2. Check YAML indentation so `description` is a sibling of `kind`, `source`, and `commands`
3. Validate the config with the toolbox binary before deploying

Example fix

# before
my-redis-tool:
  kind: redis
  source: redis-src
  commands: [["PING"]]
# after
my-redis-tool:
  kind: redis
  source: redis-src
  description: Runs the given Redis commands and returns the results.
  commands: [["PING"]]

// pre-validate the redis tool entry before handing it to the toolbox
var check struct {
	Description string `yaml:"description"`
}
if err := yaml.Unmarshal(rawToolYAML, &check); err != nil || check.Description == "" {
	return fmt.Errorf("redis tool %q: description is required and must be non-empty", toolName)
}

if err := server.Start(ctx); err != nil {
	if strings.Contains(err.Error(), "description is required") {
		log.Fatalf("config error: every tool needs a non-empty description; failing entry: %v", err)
	}
	return err
}

When it happens

Trigger: Calling Initialize during server startup for a `kind: redis` tool whose YAML entry omits the `description:` field or sets it to an empty string.

Common situations: Hand-writing a redis tool entry and forgetting the description; config generators emitting empty descriptions; YAML indentation placing `description` under the wrong key so it never binds.

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
• description is required for tool %q

AI-assisted analysis of googleapis/mcp-toolbox@8cc6e09de2 (2026-09-05). Data as JSON: /api/errors/ccf561a2915cb843. Report an issue: GitHub.