A practical guide to treating Google Gemini prompts as API contracts in production. Covers defining typed named inputs, enforcing strict JSON output schemas, validating model responses, handling null/empty inputs, preventing prompt injection, versioning prompts, and tracing failed runs. Includes a concrete support ticket classification example with code snippets and a production checklist.
Table of contents
How to Define Google Gemini Input and OutputStart with an input and output contractDefine Gemini inputs with named variablesUse specific variable namesWrite the Gemini prompt as a templateDefine a structured JSON outputUse Gemini structured output settings when possibleHandle null, empty, and unexpected inputsSeparate instructions from user-provided dataTest the same prompt across realistic casesTrace failed and fixed runsVersion your prompts before changing behaviorApply the same contract to Gemini agents and workflowsCommon mistakes to avoidProduction checklistFinal take1 Impression