doc/cli-guideline: Apply suggestions from code review

Thanks Valentin!

doc/manual/src/contributing/cli-guideline.md

@@ -391,45 +391,39 @@ status section, but only print warnings and errors.
 
 ## Returning future proof JSON
 
-The machine-readable JSON output should be extensible. This means that the
-structure of the JSON should support the addition of extra information in many
-places.
+The schema of JSON output should allow for backwards compatible extension. This section explains how to achieve this.
 
 Two definitions are helpful here, because while JSON only defines one "key-value"
-object, we use it to cover two use cases:
+object type, we use it to cover two use cases:
 
- - **dictionary**: a map from names to things that all have the same type. In
+ - **dictionary**: a map from names to value that all have the same type. In
    C++ this would be a `std::map` with string keys.
  - **record**: a fixed set of attributes each with their own type. In C++, this
-   would be represented by a struct.
+   would be represented by a `struct`.
 
-It is best not to mix these use cases, as that leads to incompatibilities and
-other bugs. For example, adding a record field to a dictionary breaks consumers
-that assume all JSON object fields to have the same meaning and type.
+It is best not to mix these use cases, as that may lead to incompatibilities when the schema changes. For example, adding a record field to a dictionary breaks consumers that assume all JSON object fields to have the same meaning and type.
 
 This leads to the following guidelines:
 
- - **The top-level value** (or **root** of the returned data structure) **must be a record**.
-   Without this rule, it would be impossible to add per-invocation metadata in
-   a manner that doesn't break existing consumers.
+ - The top-level (root) value must be a record.
 
- - **The value of a dictionary item must always be a record**. As an example,
-   suppose a command returns a dictionary where each key is the name of a store
-   type and each value is itself a dictionary representing settings.
+   Otherwise, one can not change the structure of a command's output.
 
- - **List items should be records**. For example, a list of strings is not an
-   extensible type, as any additions will break code that expects a list of
-   strings.
-   If the list is unordered and it has a unique key that is a string, consider
-   a dictionary instead of a list. If the order of the items needs to be
-   preserved, return a list of records.
+ - The value of a dictionary item must be a record.
 
- - **Streaming JSON should return records**. An example of a streaming JSON
-   format is "JSON lines", where multiple JSON values are streamed by putting
-   each on its own line in a text stream. These JSON values can be considered
-   top-level values or list items, and they must be records.
+   Otherwise, the item type can not be extended.
 
-Examples:
+ - List items should be records.
+
+   Otherwise, one can not change the structure of the list items.
+
+   If the order of the items does not matter, and each item has a unique key that is a string, consider representing the list as a dictionary instead. If the order of the items needs to be preserved, return a list of records.
+
+ - Streaming JSON should return records.
+
+   An example of a streaming JSON format is [JSON lines](https://jsonlines.org/), where each line represents a JSON value. These JSON values can be considered top-level values or list items, and they must be records.
+
+### Examples
 
 ```javascript
 // bad: all keys must be assumed to be store implementations