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

ValidateSource requires the tool's source to implement compatibleSource (Cloud Healthcare source with FHIR/DICOM store access). Sources of other types cannot supply the store/project/dataset context, so validation returns this error.

Source

Thrown at internal/tools/cloudhealthcare/cloudhealthcaregetfhirresource/cloudhealthcaregetfhirresource.go:104

// validate interface
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)
	}
	storeID, err := common.ValidateAndFetchStoreID(params, source.AllowedFHIRStores())
	if err != nil {
		return nil, util.NewAgentError("failed to validate store ID", err)
	}
	resType, ok := params.AsMap()[typeKey].(string)
	if !ok {
		return nil, util.NewAgentError(fmt.Sprintf("invalid or missing '%s' parameter; expected a string", typeKey), nil)
	}
	resID, ok := params.AsMap()[idKey].(string)

View on GitHub (pinned to 8cc6e09de2)

Solutions

  1. Point the tool's sourceRef at a cloudhealthcare source
  2. Fix the source kind in the YAML config
  3. Validate source-tool compatibility when loading config

Example fix

# before
source: bq_source
# after
source: healthcare_fhir
Defensive patterns

Strategy: type-guard

Validate before calling

if _, ok := source.(compatibleSource); !ok {
    return fmt.Errorf("source %T is not a Cloud Healthcare source", source)
}

Type guard

func isCompatibleFHIRSource(s sources.Source) bool {
    _, ok := s.(compatibleSource)
    return ok
}

Prevention

When it happens

Trigger: Calling ValidateSource with a sources.Source that does not satisfy the compatibleSource interface.

Common situations: Tool YAML sourceRef pointing at a non-healthcare source; source kind changes after migration; test harnesses using simplified source fakes.

Related errors

AI-assisted analysis of googleapis/mcp-toolbox@8cc6e09de2 (2026-09-05). Data as JSON: /api/errors/cffd302f88b5990f. Report an issue: GitHub.