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

Set the tool's source field to a compatible bigtable source in tools.yaml

source is not compatible with the tool

Error message

source is not compatible with the tool

What it means

Thrown by the bigtableupdatecluster Tool.ValidateSource when the supplied sources.Source does not implement the tool's compatibleSource interface. The tool refuses to run against a source it cannot use, before any Bigtable API call is made.

Source

Thrown at internal/tools/bigtable/bigtableupdatecluster/bigtableupdatecluster.go:96

			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.UpdateCluster(ctx, paramsMap["instance_id"].(string), paramsMap["cluster_id"].(string), int32(paramsMap["serve_nodes"].(int)))
	if err != nil {

View on GitHub (pinned to 8cc6e09de2)

Solutions

Set the tool's source field to a compatible bigtable source in tools.yaml
Confirm the referenced source initializes successfully as a Bigtable source
Restart the toolbox to reload the corrected configuration
If invoking programmatically, pass the correct concrete Source type satisfying compatibleSource

Example fix

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

Defensive patterns

Strategy: type-guard

Validate before calling

// Assert source-tool compatibility before invoking
if err := tool.ValidateSource(mySource); err != nil {
    return fmt.Errorf("cannot attach source %s to bigtable-update-cluster: %w", sourceName, err)
}

Type guard

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

Prevention

Use Bigtable sources for bigtable-update-* tools
Run config validation before deploying the toolbox
Audit tools.yaml after every source rename or deletion
Keep one source per kind and reference them explicitly

When it happens

Trigger: Invoke/ValidateSource receives a source whose concrete type fails the type assertion to bigtableupdatecluster's compatibleSource — i.e. the tool is wired to a source that is not a compatible Bigtable source in tools.yaml.

Common situations: Pointing the bigtable-update-cluster tool at a non-Bigtable source; reusing a tool config template across sources of different kinds; renaming or replacing a source and missing the tool reference.

Related errors

AI-assisted analysis of googleapis/mcp-toolbox@8cc6e09de2 (2026-09-05). Data as JSON: /api/errors/b28d1ee19314645c. Report an issue: GitHub.