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 for alloydb-alloydbcreateuser asserts the bound source implements compatibleSource (an AlloyDB admin source exposing UseClientAuthorization and GetDefaultProject). A source of any other type fails the assertion and produces this error, blocking the user-creation tool from running against an unsupported source.

Source

Thrown at internal/tools/alloydb/alloydbcreateuser/alloydbcreateuser.go:101

}

// Tool represents the create-user 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
}

// Invoke executes the tool's logic.
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()
	project, ok := paramsMap["project"].(string)
	if !ok || project == "" {
		return nil, util.NewAgentError("invalid or missing 'project' parameter; expected a non-empty string", nil)
	}

	location, ok := paramsMap["location"].(string)
	if !ok || location == "" {

View on GitHub (pinned to 8cc6e09de2)

Solutions

1. Set `source` to a kind: alloydb admin source
2. Verify the referenced source's kind in the YAML `sources:` block
3. Restart and confirm clean tool registration in the logs

Example fix

// before
source: postgres-prod
// after
source: alloydb-admin-prod

if err := tool.ValidateSource(src); err != nil {
  log.Fatal(err)
}

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

if err := tool.ValidateSource(src); err != nil {
  return fmt.Errorf("bad source for create-user: %w", err)
}

When it happens

Trigger: alloydb-alloydbcreateuser configured with a `source` that is not the AlloyDB admin source; triggered during startup validation or right before Invoke.

Common situations: Pointing the tool at an alloydb-postgres or postgres source; template reuse where `source:` wasn't updated; a typo landing on the wrong source entry.

Related errors

• invalid source for %q tool: source %q is not a compatible ty
• invalid source for %q tool: source %q is not a compatible ty
• error getting parameters for tool: %w
• error creating AlloyDB instance: %w
• error creating AlloyDB user: %w

AI-assisted analysis of googleapis/mcp-toolbox@8cc6e09de2 (2026-09-05). Data as JSON: /api/errors/48bce4b0f9dba0ac. Report an issue: GitHub.