googleapis/mcp-toolbox · error

source is not compatible with the tool

Error message

source is not compatible with the tool

What it means

bigtable-list-clusters' ValidateSource emits this error when the passed source cannot be asserted to compatibleSource (which requires ListClusters(context.Context) (any, error) semantics on the Bigtable source type). Because sources are resolved by name at runtime, any non-Bigtable source bound to this admin tool fails. This is purely a compatibility check ahead of the actual instance-admin call.

Source

Thrown at internal/tools/bigtable/bigtablelistclusters/bigtablelistclusters.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.ListClusters(ctx, paramsMap["instance_id"].(string))
	if err != nil {

View on GitHub (pinned to 8cc6e09de2)

Solutions

  1. Bind bigtable-list-clusters to a source declared with kind: bigtable
  2. Confirm the source implements the tool's compatibleSource method set
  3. Rebuild config and restart so tool/source registration matches
  4. Add an automated config-lint step in CI that checks tool-source kinds

Example fix

// before
kind: bigtable-list-clusters
source: spanner-src
// after
kind: bigtable-list-clusters
source: bigtable-src
Defensive patterns

Strategy: validation

Validate before calling

if err := tool.ValidateSource(src); err != nil {
    return fmt.Errorf("bigtable-list-clusters requires a bigtable source: %w", err)
}

Type guard

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

Try / catch

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

Prevention

When it happens

Trigger: Invoking the list-clusters tool, or calling ValidateSource directly, with a source of a different engine kind or a Bigtable source lacking the ListClusters method in the current version.

Common situations: tools.yaml maps the tool to a SQL source; a source was renamed/re-pointed during refactoring; a custom source implementation is missing the admin method set.

Related errors

AI-assisted analysis of googleapis/mcp-toolbox@8cc6e09de2 (2026-09-05). Data as JSON: /api/errors/9ee8a44001170c79. Report an issue: GitHub.