ChatGPT connector returns empty {} for MCP tool results with type: "image" while same tool works in MCP Inspector

This looks like an integration-surface mismatch rather than an invalid MCP tool result.

MCP image blocks like { type: "image", data: "<raw base64>", mimeType: "image/png" } are valid MCP, which is why MCP Inspector can render them. However, ChatGPT connector/app output should not currently be treated as a guaranteed “tool-returned image becomes model-visible vision input” path.

For ChatGPT, return model-readable output as content text and/or structuredContent. If you return only an image block, the visible structured body may appear as {}.

Recommended workaround:

• Keep the image block if you want clients that support MCP images to render it.

• Also return a text summary and structuredContent.

• If the model needs to analyze the screenshot, have your MCP tool call the Responses API with the screenshot as input_image, then return the analysis as text/JSON.

Hope this helps!