I was attempting to create a datapack function for displaying held item in chat and ran into a following incompatiblity with using macros in tellraw.

My setup is the following:

showitem.mcfunction:

$tellraw @a[distance=..16] [{"text":"$(id)","hoverEvent":{"action":"show_item","contents":{"id":"$(id)","count":"$(count)","components":$(components)}}}] 

command:

function test:showitem with entity @s SelectedItem 

Running the above command throws the following error:
_{caused error: Invalid chat component: Use JsonReader.setLenient(true) to accept malformed JSON}

To see what the macro was turning into I changed the function to use say command instead and this is the returned json:

[{"text":"minecraft:written_book","hoverEvent":{"action":"show_item","contents":{"id":"minecraft:written_book","count":"1","components":{"minecraft:written_book_content":{author:"Lare",generation:3,title:{raw:""}}}}}}] 

Whatever the macro inserted in the components isn't in the strict JSON format and hence is not compatible with tellraw.