monzo tagger will run through your transactions and apply rules based on the conditions you set

Haven’t tested a direct debit specifically but you can add notes/tags to transactions by using the annotate transaction request with the key “notes” https://docs.monzo.com/#annotate-transaction

• auth to monzo api
• get list of all transactions
• create all conditions
• create all actions
• run each transaction through the conditions
• apply each action
• annotate transaction to say that it has been run through a ruleset
• create tests