Why Free AI Inference Models Should Never Define Your API Contracts

Software teams increasingly rely on free-tier AI inference models to fill gaps in API design, but this practice carries hidden risks when those models are allowed to define authoritative contracts or wire formats. Free models may invent plausible-looking headers, error codes, and field names that never exist in production, causing failures that surface only during incidents rather than in tests. The article argues that free inference belongs in an isolated 'sketch lane' for exploratory tasks like prompt testing and throwaway prototypes, not in directories or workflows that other teams will integrate against. Key red flags include tasks that define wire formats, draft customer-facing copy, or require bit-identical reproducibility over time. The recommended safeguard is a strict preflight gate: if output targets a contracts directory or fails schema validation, the process stops rather than adapting the schema to match the model's invention.