googleapis/mcp-toolbox · error

unable to parse as %q: %w

Error message

unable to parse as %q: %w

What it means

The strict decoder rejected the embedding model config body: dec.DecodeContext into gemini.Config failed. This typically means an unknown field (strict mode), a wrong-typed field, or a missing required field inside the embedding model entry.

Source

Thrown at internal/server/config.go:451

		return nil, fmt.Errorf("%s is not a valid type of auth service", resourceType)
	}
}

func UnmarshalYAMLEmbeddingModelConfig(ctx context.Context, name string, r map[string]any) (embeddingmodels.EmbeddingModelConfig, error) {
	resourceType, ok := r["type"].(string)
	if !ok {
		return nil, fmt.Errorf("missing 'type' field or it is not a string")
	}
	if resourceType != gemini.EmbeddingModelType {
		return nil, fmt.Errorf("%s is not a valid type of embedding model", resourceType)
	}
	dec, err := util.NewStrictDecoder(r)
	if err != nil {
		return nil, fmt.Errorf("error creating decoder: %s", err)
	}
	actual := gemini.Config{Name: name}
	if err := dec.DecodeContext(ctx, &actual); err != nil {
		return nil, fmt.Errorf("unable to parse as %q: %w", name, err)
	}
	return actual, nil
}

func UnmarshalYAMLToolConfig(ctx context.Context, name string, r map[string]any) (tools.ToolConfig, error) {
	err := NameValidation(name)
	if err != nil {
		return nil, err
	}
	resourceType, ok := r["type"].(string)
	if !ok {
		return nil, fmt.Errorf("missing 'type' field or it is not a string")
	}
	// `authRequired` and `useClientOAuth` cannot be specified together
	if r["authRequired"] != nil && r["useClientOAuth"] == true {
		return nil, fmt.Errorf("`authRequired` and `useClientOAuth` are mutually exclusive. Choose only one authentication method")
	}
	// Make `authRequired` an empty list instead of nil for Tool manifest

View on GitHub (pinned to 8cc6e09de2)

Solutions

  1. Read the wrapped error after 'unable to parse as' for the exact offending field
  2. Remove or rename unknown/misspelled fields — decoding is strict
  3. Compare against the documented gemini embedding model example config

Example fix

// before
embeddingModels:
  my-embed:
    type: gemini
    modle: text-embedding-004
// after
embeddingModels:
  my-embed:
    type: gemini
    model: text-embedding-004
Defensive patterns

Strategy: validation

Validate before calling

allowed := map[string]bool{"type": true, "name": true, "model": true, "apiVersion": true, "description": true}
func checkUnknownFields(cfg map[string]any, allowed map[string]bool) []string {
  var bad []string
  for k := range cfg { if !allowed[k] { bad = append(bad, k) } }
  return bad
}

Try / catch

cfg, err := server.UnmarshalYAMLEmbeddingModelConfig(ctx, name, raw)
if err != nil {
  log.Printf("gemini embedding model %q rejected: %v — check for unknown/misspelled fields", name, err)
  return err
}

Prevention

When it happens

Trigger: An embeddingModels entry with `type: gemini` but containing an unrecognized key (strict decoding), a field of the wrong type (e.g. apiVersion: 2), or a required gemini.Config field that failed validation.

Common situations: Typos in field names like `apiVersion` -> `apiversion`; pasting LLM-model fields (temperature, etc.) that do not exist on the embedding model config; wrong indentation making a sibling key part of the model entry.

Understand the failure class

Background: Schema validation failed / invalid input schema: payload rejected because its shape doesn't match the expected schema — this error's family across 28 libraries.

Related errors

AI-assisted analysis of googleapis/mcp-toolbox@8cc6e09de2 (2026-09-05). Data as JSON: /api/errors/6d58572938b1a157. Report an issue: GitHub.