googleapis/mcp-toolbox · error

invalid source for %q tool: source %q is not a compatible ty

Error message

invalid source for %q tool: source %q is not a compatible type

What it means

The dataplexgetdatainsights tool's ValidateSource returns this error when the injected sources.Source does not satisfy the tool's private `compatibleSource` interface (a GetDataInsights method). This is a fail-fast guard: the type assertion `source.(compatibleSource)` fails, so the tool reports that the source is not a compatible type rather than attempting an API call. It indicates a tool-to-source wiring mismatch, not a Dataplex API problem.

Source

Thrown at internal/tools/dataplex/dataplexgetdatainsights/dataplexgetdatainsights.go:99

var _ tools.Tool = Tool{}

type Tool struct {
	tools.BaseTool[Config]
}

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

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

func (t Tool) ValidateSource(source sources.Source) error {
	_, ok := source.(compatibleSource)
	if !ok {
		return fmt.Errorf("invalid source for %q tool: source %q is not a compatible type", t.Cfg.Type, t.Cfg.Source)
	}
	return nil
}

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

	if scanId == "" {
		return nil, util.NewAgentError("scanId parameter is required", nil)
	}
	if location == "" {
		return nil, util.NewAgentError("location parameter is required", nil)

View on GitHub (pinned to 8cc6e09de2)

Solutions

  1. Configure the tool with a `source` that is a Dataplex source implementing GetDataInsights.
  2. Compare your source's method set against the compatibleSource interface in internal/tools/dataplex/dataplexgetdatainsights/dataplexgetdatainsights.go.
  3. Add or fix the GetDataInsights method on your custom source to match the interface exactly.
  4. Rebuild/redeploy with a current source implementation if the interface drifted.

Example fix

// before: test stub missing method
// type fakeSource struct{}
// func (f fakeSource) SourceType() string { return "dataplex" }
//
// after
// type fakeSource struct{}
// func (f fakeSource) SourceType() string { return "dataplex" }
// func (f fakeSource) GetDataInsights(ctx context.Context, /* params */) (*dataplex.Facet, error) { ... }
Defensive patterns

Strategy: type-guard

Validate before calling

if _, ok := src.(interface {
	GetDataInsights(ctx context.Context, /* params */) (*dataplex.Facet, error)
}); !ok {
	return errors.New("source does not support dataplex-get-data-insights")
}

Type guard

func isGetDataInsightsSource(s sources.Source) bool {
	_, ok := s.(dataplexgetdatainsights.CompatibleSource)
	return ok
}

Try / catch

defer func() {
	if r := recover(); r != nil { /* not needed: ValidateSource returns error */ }
}()
if err := tool.ValidateSource(src); err != nil {
	return nil, fmt.Errorf("swap to a dataplex source: %w", err)
}

Prevention

When it happens

Trigger: Passing any sources.Source to ValidateSource that lacks the GetDataInsights method signature required by this tool's compatibleSource interface — e.g., wiring the tool to a non-Dataplex source in the YAML config, or supplying a mock in tests.

Common situations: Copy-pasted tool configs referencing the wrong source name; a custom source implementation missing the GetDataInsights method; interface drift after refactoring the source's method signature; running an old binary where the source kind was registered differently.

Related errors

AI-assisted analysis of googleapis/mcp-toolbox@8cc6e09de2 (2026-09-05). Data as JSON: /api/errors/91f5bc9a1c53879e. Report an issue: GitHub.