4.1. add
The "add" operation performs one of the following functions,
depending upon what the target location references:
o If the target location specifies an array index, a new value is
inserted into the array at the specified index.
o If the target location specifies an object member that does not
already exist, a new member is added to the object.
o If the target location specifies an object member that does exist,
that member's value is replaced.
The operation object MUST contain a "value" member whose content
specifies the value to be added.
For example:
{ "op": "add", "path": "/a/b/c", "value": [ "foo", "bar" ] }
When the operation is applied, the target location MUST reference one
of:
o The root of the target document - whereupon the specified value
becomes the entire content of the target document.
o A member to add to an existing object - whereupon the supplied
value is added to that object at the indicated location. If the
member already exists, it is replaced by the specified value.
o An element to add to an existing array - whereupon the supplied
value is added to the array at the indicated location. Any
elements at or above the specified index are shifted one position
to the right. The specified index MUST NOT be greater than the
number of elements in the array. If the "-" character is used to
index the end of the array (see [RFC6901]), this has the effect of
appending the value to the array.
Because this operation is designed to add to existing objects and
arrays, its target location will often not exist. Although the
pointer's error handling algorithm will thus be invoked, this
specification defines the error handling behavior for "add" pointers
to ignore that error and add the value as specified.
However, the object itself or an array containing it does need to
exist, and it remains an error for that not to be the case. For
example, an "add" with a target location of "/a/b" starting with this
document:
{ "a": { "foo": 1 } }
is not an error, because "a" exists, and "b" will be added to its
value. It is an error in this document:
{ "q": { "bar": 2 } }
because "a" does not exist.
and here is similar for remove
4.2. remove
The "remove" operation removes the value at the target location.
The target location MUST exist for the operation to be successful.
For example:
{ "op": "remove", "path": "/a/b/c" }
If removing an element from an array, any elements above the
specified index are shifted one position to the left.
The TLDR is that to add an item to an array, you must provide the array index in the path. For example, the below payload will add the HELPDESK capability at the beginning of the capabilities array.