Notifio is a tool designed to automate responding to rental listings in competitive markets. Its primary function is to quickly fill out contact forms on new listings to ensure early replies. A key challenge in developing this feature is accurately identifying and avoiding payment-related pages. Textually, rental listing pages and pages requiring payment can be very similar, quoting prices and offering buttons to initiate contact. However, the cost of error is asymmetric: missing a valid listing is less severe than accidentally signing a user up for an unwanted subscription.To prevent this, Notifio employs cautious, deterministic guards rather than AI models, ensuring predictable and explainable refusals. An initial approach using keywords like "iDEAL" proved problematic, as it could falsely flag legitimate listing sites containing similar terms. Instead, Notifio now checks for specific payment service provider script hosts or card field HTML attributes, focusing on the page's underlying technical structure rather than its human-readable text. For subscription pages, a subtler detection method is used, looking for prices quoted per month with a limited number of digits. Domain knowledge is crucial here, as rental listings typically have higher prices than subscription fees, preventing accidental blockages.Every refusal is meticulously recorded with a specific reason, categorized into seven distinct statuses like "skipped_payment" or "skipped_captcha." This detailed logging helps users understand why their automated responses may not have been sent. The system prioritizes refusals by severity, starting with off-domain links and progressing through payment issues, anti-bot measures, and login/signup walls. The goal is to provide clear explanations for any automated action or inaction.