diff --git a/api-specs/api/resources/orders.raml b/api-specs/api/resources/orders.raml
index 3779ac01f..7c54a6b6a 100644
--- a/api-specs/api/resources/orders.raml
+++ b/api-specs/api/resources/orders.raml
@@ -334,7 +334,9 @@ post:
             type: OrderPagedSearchResponse
   head:
     securedBy: [oauth_2_0: { scopes: ['view_orders:{projectKey}'] }]
-    description: Checks whether a search index for the Project's Orders exists.
+    description: |
+      Checks whether a search index for the Project's Orders exists.
+      Returns a `200 OK` status if the index exists or a `404 Not Found` error otherwise.
     responses:
       200:
         description: The index exists and the Search Orders endpoint can be used.
diff --git a/api-specs/api/types/order-search/OrderSearchCustomType.raml b/api-specs/api/types/order-search/OrderSearchCustomType.raml
new file mode 100644
index 000000000..5aefeaae0
--- /dev/null
+++ b/api-specs/api/types/order-search/OrderSearchCustomType.raml
@@ -0,0 +1,58 @@
+#%RAML 1.0 DataType
+(package): Order
+displayName: OrderSearchCustomType
+description: Possible values for the `customType` property on [query expressions](/../api/projects/order-search#query-expressions) indicating the data type of the `field`.
+type: string
+enum:
+  - BooleanType
+  - StringType
+  - LocalizedStringType
+  - EnumType
+  - LocalizedEnumType
+  - NumberType
+  - DateType
+  - TimeType
+  - DateTimeType
+  - SetType.StringType
+  - SetType.LocalizedStringType
+  - SetType.EnumType
+  - SetType.LocalizedEnumType
+  - SetType.NumberType
+  - SetType.DateType
+  - SetType.TimeType
+  - SetType.DateTimeType
+(enumDescriptions):
+  BooleanType: |
+    For [CustomFieldBooleanType](ctp:api:type:CustomFieldBooleanType) Custom Fields.
+  StringType: |
+    For [CustomFieldStringType](ctp:api:type:CustomFieldStringType) Custom Fields.
+  LocalizedStringType: |
+    For [CustomFieldLocalizedStringType](ctp:api:type:CustomFieldLocalizedStringType) Custom Fields.
+  EnumType: |
+    For [CustomFieldEnumType](ctp:api:type:CustomFieldEnumType) Custom Fields.
+  LocalizedEnumType: |
+    For [CustomFieldLocalizedEnumType](ctp:api:type:CustomFieldLocalizedEnumType) Custom Fields.
+  NumberType: |
+    For [CustomFieldNumberType](ctp:api:type:CustomFieldNumberType) Custom Fields.
+  DateType: |
+    For [CustomFieldDateType](ctp:api:type:CustomFieldDateType) Custom Fields.
+  DateTimeType: |
+    For [CustomFieldDateTimeType](ctp:api:type:CustomFieldDateTimeType) Custom Fields.
+  TimeType: |
+    For [CustomFieldTimeType](ctp:api:type:CustomFieldTimeType) Custom Fields.
+  SetType.StringType: |
+    For [CustomFieldSetType](ctp:api:type:CustomFieldSetType) of `StringType` Custom Fields.
+  SetType.LocalizedStringType: |
+    For [CustomFieldSetType](ctp:api:type:CustomFieldSetType) of `LocalizedStringType` Custom Fields.
+  SetType.EnumType: |
+    For [CustomFieldSetType](ctp:api:type:CustomFieldSetType) of `EnumType` Custom Fields.
+  SetType.LocalizedEnumType: |
+    For [CustomFieldSetType](ctp:api:type:CustomFieldSetType) of `LocalizedEnumType` Custom Fields.
+  SetType.NumberType: |
+    For [CustomFieldSetType](ctp:api:type:CustomFieldSetType) of `NumberType` Custom Fields.
+  SetType.DateType: |
+    For [CustomFieldSetType](ctp:api:type:CustomFieldSetType) of `DateType` Custom Fields.
+  SetType.DateTimeType: |
+    For [CustomFieldSetType](ctp:api:type:CustomFieldSetType) of `DateTimeType` Custom Fields.
+  SetType.TimeType: |
+    For [CustomFieldSetType](ctp:api:type:CustomFieldSetType) of `TimeType` Custom Fields.
diff --git a/api-specs/api/types/order-search/OrderSearchQueryExpressionValue.raml b/api-specs/api/types/order-search/OrderSearchQueryExpressionValue.raml
index 439774ec9..f374f92fd 100644
--- a/api-specs/api/types/order-search/OrderSearchQueryExpressionValue.raml
+++ b/api-specs/api/types/order-search/OrderSearchQueryExpressionValue.raml
@@ -10,4 +10,4 @@ properties:
     type: number
     format: int32
   customType?:
-    type: string
+    type: OrderSearchCustomType
diff --git a/api-specs/api/types/order/OrderSearchRequest.raml b/api-specs/api/types/order/OrderSearchRequest.raml
index ccb1eea8f..fb8a7c1c5 100644
--- a/api-specs/api/types/order/OrderSearchRequest.raml
+++ b/api-specs/api/types/order/OrderSearchRequest.raml
@@ -15,10 +15,10 @@ properties:
     format: int32
     default: 10
     maximum: 100
-    description: The maximum number of search results to be returned.
+    description: The maximum number of search results to be returned on one [page](#pagination).
   offset?:
     type: number
     format: int32
     default: 0
     maximum: 10000
-    description: The number of search results to be skipped in the response for pagination.
+    description: The number of search results to be skipped in the response for [pagination](#pagination).
diff --git a/api-specs/api/types/types.raml b/api-specs/api/types/types.raml
index 457368ffa..b067f40f5 100644
--- a/api-specs/api/types/types.raml
+++ b/api-specs/api/types/types.raml
@@ -1475,6 +1475,7 @@ OrderPagedSearchResponse: !include order-search/OrderPagedSearchResponse.raml
 OrderSearchAndExpression: !include order-search/OrderSearchAndExpression.raml
 OrderSearchAnyValue: !include order-search/OrderSearchAnyValue.raml
 OrderSearchCompoundExpression: !include order-search/OrderSearchCompoundExpression.raml
+OrderSearchCustomType: !include order-search/OrderSearchCustomType.raml
 OrderSearchDateRangeExpression: !include order-search/OrderSearchDateRangeExpression.raml
 OrderSearchDateRangeValue: !include order-search/OrderSearchDateRangeValue.raml
 OrderSearchExactExpression: !include order-search/OrderSearchExactExpression.raml