@Benjamin De Boe have you tried something like below? That worked for me (partially). The tables I'm dealing with have a fair number of fields so I was running into the too large prompt issue too. I had to give a break from exploring further

db = SQLDatabase.from_uri(connection_string, schema="HSAA",include_tables=['Episode','Patient']

@Alex Woodhead, please to say that a fix was introduced to sqlalchemy-iris removing trailing semi-colons

Thanks @Dmitry Maslennikov 

Great one!