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 type-asserts the resolved source against the tool's compatibleSource interface (RunSQL over pgx). The error fires when the tool is bound to a source that is not a Postgres-compatible source, i.e. the tool kind and source kind in the YAML configuration are incompatible.

Source

Thrown at internal/tools/postgres/postgresgetcolumncardinality/postgresgetcolumncardinality.go:141

	resp, err := source.RunSQL(ctx, getColumnCardinality, sliceParams)
	if err != nil {
		return nil, util.ProcessGeneralError(err)
	}
	return resp, nil
}

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
}

View on GitHub (pinned to 8cc6e09de2)

Solutions

1. Point the tool's 'source' field at a Postgres-compatible source (e.g. postgres, cloudsql-postgres, alloydb-postgres) defined in tools.yaml
2. Ensure the source kind implements RunSQL over pgx/v5
3. Correct any typo in the source name that resolved to the wrong source

When it happens

Trigger: Thrown at internal/tools/postgres/postgresgetcolumncardinality/postgresgetcolumncardinality.go:141 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of googleapis/mcp-toolbox@8cc6e09de2 (2026-09-05). Data as JSON: /api/errors/a19cb8fa4e3fd5be. Report an issue: GitHub.