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

Bind the tool to a source with kind: bigtable in tools.yaml

source is not compatible with the tool

Error message

source is not compatible with the tool

What it means

The bigtable-get-logical-view tool's ValidateSource returns this error when the supplied sources.Source cannot be asserted to its compatibleSource interface, which requires a GetLogicalView(context.Context, string) (any, error) method. The toolbox resolves sources dynamically, so only the genuine Bigtable source satisfies the assertion. This indicates the tool was wired to an incompatible source, not a Bigtable data problem.

Source

Thrown at internal/tools/bigtable/bigtablegetlogicalview/bigtablegetlogicalview.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.GetLogicalView(ctx, paramsMap["instance_id"].(string), paramsMap["logical_view_id"].(string))
	if err != nil {

View on GitHub (pinned to 8cc6e09de2)

Solutions

Bind the tool to a source with kind: bigtable in tools.yaml
Confirm the source type implements the tool's expected method (GetLogicalView) for your toolbox version
Regenerate or fix the config; restart the server so sources re-register
Add a startup config validation step to fail fast on mismatched tool/source pairs

Example fix

// before (tools.yaml)
source: my-alloydb-source
// after
source: my-bigtable-source

Defensive patterns

Strategy: validation

Validate before calling

if err := tool.ValidateSource(mySource); err != nil {
    return fmt.Errorf("bigtable-get-logical-view requires a bigtable source: %w", err)
}

Type guard

func isBigtableLogicalViewSource(s sources.Source) bool {
    _, ok := s.(interface{ GetLogicalView(context.Context, string) (any, error) })
    return ok
}

Try / catch

if err := tool.ValidateSource(src); err != nil {
    log.Fatalf("wrong source for bigtable-get-logical-view: %v", err)
}

Prevention

Verify the 'source:' key under each tool points at a bigtable source
Validate merged configs at startup
Avoid mixing prebuilt bigtable tools with custom non-bigtable sources
Re-check tool/source bindings after toolbox upgrades

When it happens

Trigger: ValidateSource is called, or the tool is invoked via the MCP/API server, with a non-Bigtable source (e.g. postgres, spanner) or a source missing the GetLogicalView method required by this tool version.

Common situations: Wrong source name in the tool's yaml config; a source defined with the wrong kind; mixing a custom source implementation with a prebuilt bigtable tool; version skew between toolbox releases changing source interfaces.

Related errors

AI-assisted analysis of googleapis/mcp-toolbox@8cc6e09de2 (2026-09-05). Data as JSON: /api/errors/2aa70054d9391ad5. Report an issue: GitHub.