I couldn't find this requirement in the documentation, but if you don't pass one in, you get this error:
400 {"message": "SVG generation requires 'svg.model'.",
"param": "svg.model", "code": "missing_required_parameter"}
I tried it with Sunburst with both gpt-5.5 and gpt-5.6-sol, and the results were nothing spectacular. It’s something you could already do in the ChatGPT interface by asking it to convert an existing image to an equivalent SVG.Recraft is probably the only group I know of that had a native text-to-SVG generator pretty early on, but since it’s a closed model, I’m not familiar with what they were doing under the hood technically.