googleapis/mcp-toolbox · error

failed to sample label %q: %w

Error message

failed to sample label %q: %w

What it means

Wrap inside extractNodeLabels: the sampling query that fetches a few example nodes of the named label failed, so property-shape inference for that label could not proceed.

Source

Thrown at internal/tools/falkordb/falkordbschema/falkordbschema.go:300

// property shapes from a sample of nodes.
func (t Tool) extractNodeLabels(ctx context.Context, source compatibleSource) ([]types.NodeLabel, error) {
	labelsResult, err := runReadQuery(ctx, source, "CALL db.labels()")
	if err != nil {
		return nil, fmt.Errorf("failed to list labels: %w", err)
	}

	var nodeLabels []types.NodeLabel
	for _, label := range helpers.FirstColumnStrings(labelsResult) {
		escaped := escapeIdentifier(label)

		countResult, err := runReadQuery(ctx, source, fmt.Sprintf("MATCH (n:`%s`) RETURN count(n) AS count", escaped))
		if err != nil {
			return nil, fmt.Errorf("failed to count label %q: %w", label, err)
		}

		sampleResult, err := runReadQuery(ctx, source, fmt.Sprintf("MATCH (n:`%s`) RETURN n LIMIT %d", escaped, t.Cfg.SampleSize))
		if err != nil {
			return nil, fmt.Errorf("failed to sample label %q: %w", label, err)
		}
		accumulator := make(map[string]map[string]bool)
		for _, row := range helpers.Rows(sampleResult) {
			node, ok := row["n"].(map[string]any)
			if !ok {
				continue
			}
			if properties, ok := node["properties"].(map[string]any); ok {
				helpers.MergeProperties(accumulator, properties)
			}
		}

		nodeLabels = append(nodeLabels, types.NodeLabel{
			Name:       label,
			Count:      helpers.FirstRowInt64(countResult),
			Properties: helpers.CollectProperties(accumulator),
		})
	}

View on GitHub (pinned to 8cc6e09de2)

Solutions

1. Retry the schema extraction if the graph is being mutated concurrently
2. Check server logs for the underlying query failure

When it happens

Trigger: Thrown at internal/tools/falkordb/falkordbschema/falkordbschema.go:300 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/f3c84729d1d9ab8b. Report an issue: GitHub.