googleapis/mcp-toolbox · error

bytes value must be a base64 encoded string

Error message

bytes value must be a base64 encoded string

What it means

Type-check guard in JSONToFirestoreValue for bytesValue: the value is not a string, but only a base64-encoded string can be decoded to Firestore bytes.

Source

Thrown at internal/tools/firestore/util/converter.go:82

					}
					return nil, fmt.Errorf("invalid integer value: %v", val)
				case "doubleValue":
					// Convert to float64
					switch num := val.(type) {
					case float64:
						return num, nil
					case int:
						return float64(num), nil
					case int64:
						return float64(num), nil
					}
					return nil, fmt.Errorf("invalid double value: %v", val)
				case "bytesValue":
					// Decode base64 string to bytes
					if str, ok := val.(string); ok {
						return base64.StdEncoding.DecodeString(str)
					}
					return nil, fmt.Errorf("bytes value must be a base64 encoded string")
				case "timestampValue":
					// Parse timestamp
					if str, ok := val.(string); ok {
						t, err := time.Parse(time.RFC3339Nano, str)
						if err != nil {
							return nil, fmt.Errorf("invalid timestamp format: %w", err)
						}
						return t, nil
					}
					return nil, fmt.Errorf("timestamp value must be a string")
				case "geoPointValue":
					// Convert to LatLng
					if geoMap, ok := val.(map[string]any); ok {
						lat, latOk := geoMap["latitude"].(float64)
						lng, lngOk := geoMap["longitude"].(float64)
						if latOk && lngOk {
							return &latlng.LatLng{
								Latitude:  lat,

View on GitHub (pinned to 8cc6e09de2)

Solutions

1. Encode the binary payload with standard base64 and send it as a string
2. Use stringValue instead if the data is not meant to be bytes

When it happens

Trigger: Thrown at internal/tools/firestore/util/converter.go:82 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/0775b349bc513d17. Report an issue: GitHub.