googleapis/mcp-toolbox · error

failed to unmarshal generation options to proto: %w

Error message

failed to unmarshal generation options to proto: %w

What it means

The JSON bytes produced from the YAML map are unmarshaled into the protobuf message geminidataanalyticspb.GenerationOptions using protojson. This error fires when keys or value shapes do not match the proto schema (protojson validates field names and types strictly, unlike plain JSON decoding).

Source

Thrown at internal/tools/cloudgda/cloudgda.go:106

}

// GenerationOptions wraps geminidataanalyticspb.GenerationOptions to support YAML decoding via protojson.
type GenerationOptions struct {
	*geminidataanalyticspb.GenerationOptions
}

func (g *GenerationOptions) UnmarshalYAML(b []byte) error {
	var raw map[string]any
	if err := yaml.Unmarshal(b, &raw); err != nil {
		return fmt.Errorf("failed to unmarshal generation options from yaml: %w", err)
	}
	jsonBytes, err := json.Marshal(raw)
	if err != nil {
		return fmt.Errorf("failed to marshal generation options map: %w", err)
	}
	g.GenerationOptions = &geminidataanalyticspb.GenerationOptions{}
	if err := protojson.Unmarshal(jsonBytes, g.GenerationOptions); err != nil {
		return fmt.Errorf("failed to unmarshal generation options to proto: %w", err)
	}
	return nil
}

type Config struct {
	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 {

View on GitHub (pinned to 8cc6e09de2)

Solutions

1. Check each key in generationOptions against the GenerationOptions proto message in google.golang.org/api/geminidataanalytics/v1alpha (or matching version) and fix names/types
2. Use exact proto field names (the JSON names, typically lowerCamelCase) for all keys
3. Remove unknown keys; protojson with default options rejects them
4. Pin a matching google-api-go-client version so the proto schema matches your intended fields

Example fix

// before (unknown field 'queryMod', wrong enum type)
generationOptions:
  queryMod: "AUTO"
// after
generationOptions:
  queryMode: AUTO

import ("encoding/json"; "google.golang.org/protobuf/encoding/protojson")
func validProtoShape(b []byte, msg proto.Message) error {
	var m map[string]any
	if err := yaml.Unmarshal(b, &m); err != nil { return err }
	jb, _ := json.Marshal(m)
	return protojson.Unmarshal(jb, msg)
}

When it happens

Trigger: Using unknown field names in generationOptions (protojson rejects unknown fields by default), wrong value types for known fields (e.g. a string where an enum name or bool is expected), or mapping under a field that is not a message.

Common situations: Typos in proto field names (e.g. queryMod instead of queryMode); using camelCase vs snake_case inconsistently; copying options from a different API version whose schema changed; nesting a map where proto expects a scalar.

Related errors

• failed to unmarshal generation options from yaml: %w
• failed to marshal generation options map: %w
• 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

AI-assisted analysis of googleapis/mcp-toolbox@8cc6e09de2 (2026-09-05). Data as JSON: /api/errors/40050c20efa2198a. Report an issue: GitHub.