What causes "embeddingModel %q declared more than once" in googleapis/mcp-toolbox?

Rename one of the two embeddingModels named in the error to a unique name.

embeddingModel %q declared more than once

Error message

embeddingModel %q declared more than once

What it means

UnmarshalPrimitiveConfig rejects duplicate embeddingModel names: after unmarshaling an "embeddingModel" resource, it checks `embeddingModelConfigs[name]` and errors if the name already exists. Model names are map keys; a duplicate would silently overwrite the earlier model, so parsing fails.

Source

Thrown at internal/server/config.go:307

				toolsetGroups = make(map[string]group.GroupConfig)
			}
			if _, exists := toolsetGroups[name]; exists {
				return nil, nil, nil, nil, nil, nil, fmt.Errorf("toolset %q declared more than once", name)
			}
			toolsetGroups[name] = group.GroupConfig{Name: name, ToolNames: c.ToolNames}
		case "embeddingModel":
			c, err := UnmarshalYAMLEmbeddingModelConfig(ctx, name, resource)
			if err != nil {
				if len(file.Docs) > 1 {
					return nil, nil, nil, nil, nil, nil, fmt.Errorf("document %d: error unmarshaling %s %q: %w", docIndex, kind, name, err)
				}
				return nil, nil, nil, nil, nil, nil, fmt.Errorf("error unmarshaling %s: %w", kind, err)
			}
			if embeddingModelConfigs == nil {
				embeddingModelConfigs = make(EmbeddingModelConfigs)
			}
			if _, exists := embeddingModelConfigs[name]; exists {
				return nil, nil, nil, nil, nil, nil, fmt.Errorf("embeddingModel %q declared more than once", name)
			}
			embeddingModelConfigs[name] = c
		case "prompt":
			c, err := UnmarshalYAMLPromptConfig(ctx, name, resource)
			if err != nil {
				if len(file.Docs) > 1 {
					return nil, nil, nil, nil, nil, nil, fmt.Errorf("document %d: error unmarshaling %s %q: %w", docIndex, kind, name, err)
				}
				return nil, nil, nil, nil, nil, nil, fmt.Errorf("error unmarshaling %s: %w", kind, err)
			}
			if promptConfigs == nil {
				promptConfigs = make(PromptConfigs)
			}
			if _, exists := promptConfigs[name]; exists {
				return nil, nil, nil, nil, nil, nil, fmt.Errorf("prompt %q declared more than once", name)
			}
			promptConfigs[name] = c
		case "group":

View on GitHub (pinned to 8cc6e09de2)

Solutions

Rename one of the two embeddingModels named in the error to a unique name.
Remove the redundant duplicate model definition.
Search all `---` documents for the duplicated name.
Update toolset/tool references to point at the retained model name.

Example fix

// before
embeddingModels:
  my-embed:
    provider: gemini
    modelId: text-embedding-004
  my-embed:
    provider: gemini
    modelId: text-embedding-005
// after
embeddingModels:
  my-embed:
    provider: gemini
    modelId: text-embedding-004
  my-embed-v5:
    provider: gemini
    modelId: text-embedding-005

Defensive patterns

Strategy: validation

Validate before calling

func rawDuplicateEmbeddingModelNames(data string) []string {
    var seen, dups []string
    inSection := false
    for _, line := range strings.Split(data, "\n") {
        trimmed := strings.TrimSpace(line)
        if strings.HasPrefix(line, "embeddingModels:") { inSection = true; continue }
        if inSection && !strings.HasPrefix(line, " ") && strings.HasSuffix(trimmed, ":") && !strings.HasPrefix(trimmed, "-") { inSection = false }
        if inSection && strings.HasSuffix(trimmed, ":") && !strings.HasPrefix(trimmed, "-") {
            name := strings.TrimSuffix(trimmed, ":")
            if slices.Contains(seen, name) { dups = append(dups, name) }
            seen = append(seen, name)
        }
    }
    return dups
}

Type guard

func isDuplicateEmbeddingModelErr(err error) bool {
    return err != nil && strings.Contains(err.Error(), "embeddingModel") && strings.Contains(err.Error(), "declared more than once")
}

Try / catch

cfg, err := server.ParseConfig(ctx, yamlBytes)
if err != nil {
    if strings.Contains(err.Error(), "declared more than once") {
        return fmt.Errorf("embedding model names must be unique: %w", err)
    }
    return err
}

Prevention

Version model names (my-embed-v1, my-embed-v2) instead of reusing one name.
Grep for the model name across all documents before adding a new block.
Update any references (e.g., tool/model bindings) after renaming a model.

When it happens

Trigger: Calling ParseConfig with a YAML file (single or multi-document) that declares two `embeddingModel` resources with the same name, hitting the `exists` check on `embeddingModelConfigs`.

Common situations: Adding a second embedding model block and reusing the earlier name; merging config fragments where both define `my-embed`.

Related errors

AI-assisted analysis of googleapis/mcp-toolbox@8cc6e09de2 (2026-09-05). Data as JSON: /api/errors/a45816e410f9035f. Report an issue: GitHub.