Node.js Content Moderation API: Chat JSON Schema Without a Dedicated Endpoint

What happened

The article describes a method for content moderation using a chat-based classifier in front of invoice extraction. It emphasizes the use of a strict JSON schema to return structured moderation decisions, such as 'allow', 'review', or 'block', along with policy categories and reasons. The system avoids storing raw invoice content in logs or labels to protect sensitive data. It also discusses operational considerations like retry mechanisms, schema validation, and alert thresholds for detecting policy drift and performance issues.

Why it matters

This approach is important for AI developers and content moderation engineers who need to implement a lightweight, explainable moderation system without relying on a dedicated moderation API. It helps ensure consistent and secure handling of sensitive data like supplier invoices, while also enabling operational monitoring and alerting for system performance and policy drift.

• Use a strict JSON schema to ensure consistent and validated moderation responses.
• Avoid storing raw invoice content in logs to protect sensitive data.
• Implement retry mechanisms and HTTP status handling for robustness.
• Track metrics like queue age and review rates to detect policy drift and performance issues.
• Choose a chat-based classifier with a versioned policy vocabulary for explainability.

The bigger picture

This approach allows teams to implement a lightweight, explainable moderation system for invoice intake without relying on a dedicated moderation API. It ensures data security by avoiding the storage of raw invoice content in logs and improves operational visibility through metrics and alerting.

This article provides a practical approach to implementing a content moderation system using a chat-based classifier and strict JSON schema, suitable for invoice intake without a dedicated moderation endpoint. It emphasizes data security, operational monitoring, and explainability for effective moderation.

Technical details

• Strict JSON schema is used to constrain the response to validated fields like 'decision', 'categories', 'reason', and 'policy_version'.
• The classifier uses a chat model (e.g., deepseek-v4-flash) to return structured moderation decisions.
• The system includes retry mechanisms and HTTP status handling for robustness.
• The classifier is versioned and paired with a policy vocabulary for explainability.
• The system tracks metrics like queue age, review rates, and schema validation failures for operational insights.

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