googleapis/mcp-toolbox · error

source is not compatible with the tool

Error message

source is not compatible with the tool

What it means

The bigtable-list-materialized-views tool returns this error from ValidateSource when the passed source does not implement its private compatibleSource interface (materialized-view listing on the Bigtable source). The toolbox asserts the concrete source type per tool, so any foreign source fails. It is a pre-invocation wiring check, not a Bigtable service error.

Source

Thrown at internal/tools/bigtable/bigtablelistmaterializedviews/bigtablelistmaterializedviews.go:94

			allParameters,
		),
	}, nil
}

var _ tools.Tool = Tool{}

type Tool struct {
	tools.BaseTool[Config]
}

func (t Tool) GetSourceName() string {
	return t.Cfg.Source
}

func (t Tool) ValidateSource(src sources.Source) error {
	_, ok := src.(compatibleSource)
	if !ok {
		return fmt.Errorf("source is not compatible with the tool")
	}
	return nil
}

func (t Tool) ToConfig() tools.ToolConfig {
	return t.Cfg
}

func (t Tool) Invoke(ctx context.Context, src sources.Source, params parameters.ParamValues, accessToken tools.AccessToken) (any, util.ToolboxError) {
	source, ok := src.(compatibleSource)
	if !ok {
		return nil, util.NewClientServerError("source used is not compatible with the tool", http.StatusInternalServerError, nil)
	}

	paramsMap := params.AsMap()

	res, err := source.ListMaterializedViews(ctx, paramsMap["instance_id"].(string))
	if err != nil {

View on GitHub (pinned to 8cc6e09de2)

Solutions

  1. Bind the tool to a bigtable-kind source in tools.yaml
  2. Verify the source implements the expected method set
  3. Sync config and toolbox versions; restart the server
  4. Validate the merged config at boot and in CI

Example fix

// before
source: alloydb-src
// after
source: bigtable-src
Defensive patterns

Strategy: validation

Validate before calling

if err := tool.ValidateSource(mySource); err != nil {
    return fmt.Errorf("bigtable-list-materialized-views needs a bigtable source: %w", err)
}

Type guard

func isBigtableMaterializedViewsSource(s sources.Source) bool {
    _, ok := s.(interface{ ListMaterializedViews(context.Context) (any, error) })
    return ok
}

Try / catch

if err := tool.ValidateSource(src); err != nil {
    log.Fatalf("wrong source kind for bigtable-list-materialized-views: %v", err)
}

Prevention

When it happens

Trigger: ValidateSource is called or the tool invoked with a non-Bigtable source (SQL/warehouse sources), or a Bigtable source build lacking the required method for this version.

Common situations: Copy-pasted tool configs pointing at another engine's source; environment-specific configs diverging; toolbox upgrades changing internal source interfaces.

Related errors

AI-assisted analysis of googleapis/mcp-toolbox@8cc6e09de2 (2026-09-05). Data as JSON: /api/errors/6d802558d55e47cb. Report an issue: GitHub.