resolution -> size

Author: h0rv

docs/builtin-tools.md

@@ -353,14 +353,14 @@ assert isinstance(result.output, BinaryImage)
 
 _(This example is complete, it can be run "as is")_
 
-To control the image resolution with Gemini 3 Pro Image models, use the `resolution` parameter:
+To control the image resolution with Gemini Image models starting with `gemini-3-pro-image-preview`, use the `size` parameter:
 
 ```py {title="image_generation_google_resolution.py"}
 from pydantic_ai import Agent, BinaryImage, ImageGenerationTool
 
 agent = Agent(
     'google-gla:gemini-3-pro-image-preview',
-    builtin_tools=[ImageGenerationTool(aspect_ratio='16:9', resolution='4K')],
+    builtin_tools=[ImageGenerationTool(aspect_ratio='16:9', size='4K')],
     output_type=BinaryImage,
 )
 
@@ -383,9 +383,8 @@ For more details, check the [API documentation][pydantic_ai.builtin_tools.ImageG
 | `output_format` | ✅ | ❌ |
 | `partial_images` | ✅ | ❌ |
 | `quality` | ✅ | ❌ |
-| `size` | ✅ | ❌ |
-| `aspect_ratio` | ✅ (1:1, 2:3, 3:2) | ✅ |
-| `resolution` | ❌ | ✅ (1K, 2K, 4K) |
+| `size` | ✅ (1024x1024, 1024x1536, 1536x1024, auto) | ✅ (1K, 2K, 4K) |
+| `aspect_ratio` | ✅ (1:1, 2:3, 3:2) | ✅ (1:1, 2:3, 3:2, 3:4, 4:3, 4:5, 5:4, 9:16, 16:9, 21:9) |
 
 ## Web Fetch Tool
 

pydantic_ai_slim/pydantic_ai/builtin_tools.py

@@ -311,12 +311,13 @@ class ImageGenerationTool(AbstractBuiltinTool):
     * OpenAI Responses
     """
 
-    size: Literal['1024x1024', '1024x1536', '1536x1024', 'auto'] = 'auto'
+    size: Literal['1024x1024', '1024x1536', '1536x1024', '1K', '2K', '4K', 'auto'] = 'auto'
     """The size of the generated image.
 
     Supported by:
 
-    * OpenAI Responses
+    * OpenAI Responses: '1024x1024', '1024x1536', '1536x1024', 'auto'
+    * Google (Gemini 3 Pro Image and later): '1K', '2K', '4K'
     """
 
     aspect_ratio: ImageAspectRatio | None = None
@@ -328,14 +329,6 @@ class ImageGenerationTool(AbstractBuiltinTool):
     * OpenAI Responses (maps '1:1', '2:3', and '3:2' to supported sizes)
     """
 
-    resolution: str | None = None
-    """The resolution/size tier for generated images.
-
-    Supported by:
-
-    * Google: '1K', '2K', '4K' for Gemini 3 Pro Image and compatible models
-    """
-
     kind: str = 'image_generation'
     """The kind of tool."""
 

pydantic_ai_slim/pydantic_ai/models/google.py

@@ -362,14 +362,12 @@ def _get_tools(
                         raise UserError(
                             "`ImageGenerationTool` is not supported by this model. Use a model with 'image' in the name instead."
                         )
-                    # Build image_config from tool parameters, only including non-None values
-                    image_config_kwargs: dict[str, Any] = {}
+
+                    image_config = ImageConfigDict()
                     if tool.aspect_ratio is not None:
-                        image_config_kwargs['aspect_ratio'] = tool.aspect_ratio
-                    if tool.resolution is not None:
-                        image_config_kwargs['image_size'] = tool.resolution
-                    if image_config_kwargs:
-                        image_config = ImageConfigDict(**image_config_kwargs)
+                        image_config['aspect_ratio'] = tool.aspect_ratio
+                    if tool.size in ('1K', '2K', '4K'):
+                        image_config['image_size'] = tool.size
                 else:  # pragma: no cover
                     raise UserError(
                         f'`{tool.__class__.__name__}` is not supported by `GoogleModel`. If it should be, please file an issue.'

tests/models/test_google.py

@@ -3655,7 +3655,7 @@ async def test_google_image_generation_tool_aspect_ratio(google_provider: Google
 async def test_google_image_generation_resolution(google_provider: GoogleProvider) -> None:
     """Test that resolution parameter from ImageGenerationTool is added to image_config."""
     model = GoogleModel('gemini-3-pro-image-preview', provider=google_provider)
-    params = ModelRequestParameters(builtin_tools=[ImageGenerationTool(resolution='2K')])
+    params = ModelRequestParameters(builtin_tools=[ImageGenerationTool(size='2K')])
 
     tools, image_config = model._get_tools(params)  # pyright: ignore[reportPrivateUsage]
     assert tools is None
@@ -3665,7 +3665,7 @@ async def test_google_image_generation_resolution(google_provider: GoogleProvide
 async def test_google_image_generation_resolution_with_aspect_ratio(google_provider: GoogleProvider) -> None:
     """Test that resolution and aspect_ratio from ImageGenerationTool work together."""
     model = GoogleModel('gemini-3-pro-image-preview', provider=google_provider)
-    params = ModelRequestParameters(builtin_tools=[ImageGenerationTool(aspect_ratio='16:9', resolution='4K')])
+    params = ModelRequestParameters(builtin_tools=[ImageGenerationTool(aspect_ratio='16:9', size='4K')])
 
     tools, image_config = model._get_tools(params)  # pyright: ignore[reportPrivateUsage]
     assert tools is None

tests/models/test_model_request_parameters.py

@@ -99,7 +99,6 @@ def test_model_request_parameters_are_serializable():
                     'quality': 'auto',
                     'size': '1024x1024',
                     'aspect_ratio': None,
-                    'resolution': None,
                 },
                 {'kind': 'memory'},
                 {