What causes "source is not compatible with the tool" in googleapis/mcp-toolbox?

Point the tool's source field at a compatible bigtable source

source is not compatible with the tool

Error message

source is not compatible with the tool

What it means

Thrown by the bigtableupdateinstance Tool.ValidateSource when the provided sources.Source does not implement the tool's compatibleSource interface. It prevents the instance-update tool from operating on an incompatible source before any mutation occurs.

Source

Thrown at internal/tools/bigtable/bigtableupdateinstance/bigtableupdateinstance.go:95

			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.UpdateInstance(ctx, paramsMap["instance_id"].(string), paramsMap["display_name"].(string))
	if err != nil {

View on GitHub (pinned to 8cc6e09de2)

Solutions

Point the tool's source field at a compatible bigtable source
Verify the source name matches an initialized Bigtable source
Restart the toolbox to apply the corrected config
Pass the correct concrete Source type when invoking programmatically

Example fix

// before (tools.yaml)
tools:
  update-instance:
    kind: bigtable-update-instance
    source: my-mysql-db
// after
tools:
  update-instance:
    kind: bigtable-update-instance
    source: my-bigtable-instance

Defensive patterns

Strategy: type-guard

Validate before calling

// Verify compatibility before invoking the instance-update tool
if err := tool.ValidateSource(mySource); err != nil {
    return fmt.Errorf("source %s cannot back bigtable-update-instance", sourceName)
}

Type guard

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

Prevention

Ensure bigtable-update-instance references a bigtable source kind
Add startup config validation to catch mismatched source kinds early
Review tool source references after config refactors
Test tool initialization locally before merging config changes

When it happens

Trigger: ValidateSource/Invoke is called with a source failing the type assertion to the bigtableupdateinstance compatibleSource interface — typically a tools.yaml source reference of the wrong kind.

Common situations: Wiring bigtable-update-instance to a source of another database kind; copy-paste tool templates; config refactor that swapped source names.

Related errors

AI-assisted analysis of googleapis/mcp-toolbox@8cc6e09de2 (2026-09-05). Data as JSON: /api/errors/7cee13df94407714. Report an issue: GitHub.