GPT-5.4 vs Grok 4 for Structured Output

Structured Output (per our benchmark) measures JSON schema compliance and format adherence. Key capabilities that matter: precise response_format/structured outputs support, deterministic token-level control, safety calibration to avoid injecting malformed fields, long-context handling when schemas or examples are long, and predictable tool calling when outputs must include tool arguments. Both models expose structured outputs and response_format parameters in their supported_parameters lists, and both achieve long context=5 in our tests. Because no external benchmark is provided in the payload, our internal structured output score is the primary evidence here: GPT-5.4 scored 5/5 and Grok 4 scored 4/5. We use additional internal proxies (safety calibration, agentic planning, tool calling) as explanatory signals: GPT-5.4’s higher safety calibration (5 vs 2) and agentic planning (5 vs 3) help it avoid schema-violating content and recover from failures, which improves real-world structured-output reliability.

1. Strict API integration (billing, invoicing JSON): GPT-5.4 is preferable — scores 5 vs Grok 4’s 4 on structured output in our tests, and its safety calibration=5 reduces malformed or extra fields. 2) Complex nested schema with long examples: GPT-5.4’s long context=5 and structured output=5 help it follow long schema examples and produce compliant output. 3) Multi-step automation that selects tools and returns a JSON payload invoking them: Both models tie on tool calling=4, but Grok 4 advertises parallel tool calling (description) which can simplify multi-API workflows; choose Grok 4 if you need that parallel invocation plus slightly stronger classification (Grok 4 classification=4 vs GPT-5.4 classification=3). 4) High-assurance apps needing refusal behavior and failure recovery (medical triage, legal routing): GPT-5.4’s higher safety calibration (5 vs 2) and agentic planning (5 vs 3) make it more reliable for strict acceptance/refusal criteria. 5) Cost-aware batch processing: GPT-5.4 has lower input cost (2.5 vs 3 per mTok) which compounds when sending long schema examples — helpful for high-volume structured-output generation.

For Structured Output, choose GPT-5.4 if you need the highest schema compliance, stricter safety behavior, stronger planning/failure recovery, and slightly lower input cost (GPT-5.4: structured output=5, safety calibration=5, input cost 2.5). Choose Grok 4 if you need better built-in classification (Grok 4 classification=4) or parallel tool-calling workflows and are comfortable with a 4/5 structured output score and the model's quirks (Grok 4: structured output=4, supports parallel tool calling).