Update docs/builtin-tools.md

Co-authored-by: Douwe Maan <me@douwe.me>

Author: mwildehahn

docs/builtin-tools.md

@@ -292,7 +292,7 @@ assert isinstance(result.output, BinaryImage)
 _(This example is complete, it can be run "as is")_
 
 OpenAI Responses models also respect the `aspect_ratio` parameter. Because the OpenAI API only exposes discrete image sizes,
-PydanticAI maps `'1:1'` -> `1024x1024`, `'2:3'` -> `1024x1536`, and `'3:2'` -> `1536x1024`. Providing any other aspect ratio
+Pydantic AI maps `'1:1'` -> `1024x1024`, `'2:3'` -> `1024x1536`, and `'3:2'` -> `1536x1024`. Providing any other aspect ratio
 results in an error, and if you also set `size` it must match the computed value.
 
 To control the aspect ratio when using Gemini image models, include the `ImageGenerationTool` explicitly: