Improved wording in load_collection.

Author: m-mohr

load_collection.json

@@ -145,7 +145,7 @@
             }
         },
         "properties": {
-            "description": "Limits the data by metadata properties to include only data in the data cube which the given expressions return `true` for.\n\nSpecify key-value-pairs with the keys being the name of the metadata property, which can be retrieved with the openEO Data Discovery for Collections. The values must be expressions to be evaluated against the collection metadata, see the example.",
+            "description": "Limits the data by metadata properties to include only data in the data cube which all given expressions return `true` for (AND operation).\n\nSpecify key-value-pairs with the keys being the name of the metadata property, which can be retrieved with the openEO Data Discovery for Collections. The values must be expressions to be evaluated against the collection metadata, see the example.\n\n**Note:** Back-ends may not pass the actual value to the expressions, but pass a proprietary index or a placeholder so that they can use the expressions to query against another data source. So debugging on the callback parameter `value` may lead to unexpected results.",
             "experimental": true,
             "schema": {
                 "anyOf": [