OpenAI API — May, 2025
Significant enhancements in tool capabilities, with support for new built-in tools like a code interpreter and remote MCP servers in the Responses API. Tool schema definitions have been improved, now including strict mode for parallel calling and advanced validation features such as email patterns and range specifications for numbers and arrays. Furthermore, this release introduces support for reinforcement fine-tuning, making gpt-4.1-nano available for this method, and launches codex-mini-latest in the API for Codex CLI users.
Source: official ChatGPT & Codex release notes. Summaries are written from the official notes; see how we work.
Added
- Added support for new built-in tools in the Responses API, including remote MCP servers and code interpreter. Learn more about tools.
- Added support for using strict mode for tool schemas when using parallel tool calling with non-fine-tuned models. Added new schema features, including string validation for email and other patterns and specifying ranges for numbers and arrays.
- Launched codex-mini-latest in the API, optimized for use with the Codex CLI.
- Launched support for reinforcement fine-tuning. Learn about available fine-tuning methods. gpt-4.1-nano is now available for fine-tuning.
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