Postgrest function mapping not recognizing my json parameter

Question

My PostgrestSQL isn't recognizing my function parameter as JSON instead seems like I need to pass all the JSON entries.

I'm trying to create a new function in my PostgrestSQL that uses JSON as function argument, but then I got a problem. The problem is when I do a request to my endpoint I get this error:

{
    "hint": "No function matches the given name and argument types. You might need to add explicit type casts.",
    "details": null,
    "code": "42883",
    "message": "function rest_api.my_method(id => text) does not exist"
}

but in fact, this 'id' argument doesn't exist. Instead I'm passing a json as param. This error isn't able the function handle the body, it's throwing this error before.

That's how I wrote my function:

CREATE OR REPLACE FUNCTION rest_api.my_method(json)
    RETURNS json
    LANGUAGE 'plv8'
    COST 100
    VOLATILE PARALLEL UNSAFE
AS $BODY$
{   
    const jsonData = $1;
    return jsonData;
}
$BODY$;

if I run this query SELECT rest_api.my_method('{"key": "value"}'); it's returning the json {"key": "value"} as it should do.