JamesNK/Newtonsoft.Json · error · JsonException

Invalid JSON schema type: {0}

Error message

Invalid JSON schema type: {0}

What it means

Thrown by JsonSchemaBuilder.MapType when the 'type' field of a JSON Schema contains a string that is not in the recognized mapping (object, array, string, number, integer, boolean, null, any). The builder cannot map the token to a JsonSchemaType enum value.

Source

Thrown at Src/Newtonsoft.Json/Schema/JsonSchemaBuilder.cs:485

                            throw JsonException.Create(typeToken, typeToken.Path, "Expected JSON schema type string token, got {0}.".FormatWith(CultureInfo.InvariantCulture, token.Type));
                        }

                        type = type | MapType((string)typeToken);
                    }

                    return type;
                case JTokenType.String:
                    return MapType((string)token);
                default:
                    throw JsonException.Create(token, token.Path, "Expected array or JSON schema type string token, got {0}.".FormatWith(CultureInfo.InvariantCulture, token.Type));
            }
        }

        internal static JsonSchemaType MapType(string type)
        {
            if (!JsonSchemaConstants.JsonSchemaTypeMapping.TryGetValue(type, out JsonSchemaType mappedType))
            {
                throw new JsonException("Invalid JSON schema type: {0}".FormatWith(CultureInfo.InvariantCulture, type));
            }

            return mappedType;
        }

        internal static string MapType(JsonSchemaType type)
        {
            return JsonSchemaConstants.JsonSchemaTypeMapping.Single(kv => kv.Value == type).Key;
        }
    }
}

View on GitHub (pinned to 4f73e74372)

Solutions

1. Use one of the valid JSON Schema type strings: object, array, string, number, integer, boolean, null, any.
2. Map language types to schema types before emitting (e.g. int/double -> number/integer).
3. Upgrade to the separate Newtonsoft.Json.Schema package if you need newer draft type semantics.

Example fix

// before
JsonSchema.Parse("{\"type\":\"double\"}");
// after
JsonSchema.Parse("{\"type\":\"number\"}");

static readonly HashSet<string> ValidTypes = new()
{ "object","array","string","number","integer","boolean","null","any" };
static bool IsValidType(string type) => ValidTypes.Contains(type);

try { JsonSchema.Parse(json); }
catch (JsonException ex) when (ex.Message.StartsWith("Invalid JSON schema type"))
{ /* map language type names to schema type names before parsing */ }

When it happens

Trigger: A schema with an unrecognized type value. Examples: JsonSchema.Parse("{\"type\":\"double\"}") (should be 'number'), "{\"type\":\"int\"}" (should be 'integer'), "{\"type\":\"datetime\"}", or a typo like 'strnig'.

Common situations: Using draft-4+ type names not supported by the legacy draft-3 builder; typos; mapping from a different schema dialect; auto-generated schemas using language type names (int, long, double) instead of JSON Schema type names.

Understand the failure class

• Parsing and encoding errors: unexpected token, malformed input — why parsers reject input and how to find the real culprit.

Related errors

• Property {0} has already been defined in schema.
• Could not resolve schema reference '{0}'.
• Unresolved circular reference for type '{0}'. Explicitly def
• Unexpected contract type: {0}
• Newtonsoft.Json serialization is not compatible with trimmin

AI-assisted analysis of JamesNK/Newtonsoft.Json@4f73e74372 (2026-08-07). Data as JSON: /api/errors/d1df1c3f681ab052. Report an issue: GitHub.