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Copy file name to clipboardExpand all lines: docs/servers/media.md
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@@ -6,17 +6,17 @@ The SDK ships two helpers for binary results (**`Image`** and **`Audio`**) and a
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## Returning an image
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Annotate the return type as `Image`and return one:
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Annotate the return type as `Image`, point it at a file, and return it:
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```python title="server.py" hl_lines="14 16"
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```python title="server.py" hl_lines="8 12 14"
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--8<--"docs_src/media/tutorial001.py"
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```
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*`Image` takes exactly one of `data` (raw bytes) or `path` (a file to read).
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*`format="png"` becomes the MIME type the client sees:`image/png`.
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*The bytes here are a one-pixel placeholder so the file runs on its own. In a real server they come from Pillow, matplotlib, a headless browser, or anything else that hands you `bytes`.
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*`Image` takes exactly one of `path` (a file to read) or `data` (raw bytes).
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*The MIME type the client sees is guessed from the suffix: `logo.png` is announced as`image/png`.
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*Nothing here is special about logos. Any PNG next to `server.py` works: a chart your code rendered, a diagram, a photo.
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`Image` is an SDK convenience, not a protocol type. On the wire your return value becomes an **`ImageContent`** block (your bytes base64-encoded, plus the MIME type):
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`Image` is an SDK convenience, not a protocol type. On the wire your return value becomes an **`ImageContent`** block (the file's bytes base64-encoded, plus the MIME type):
*`data` is base64. You returned raw `bytes`; the SDK did the encoding.
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*`data` is base64. You never touched the bytes; the SDK read the file and did the encoding.
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*`structured_content` is `None`. An `Image` is content for the model to look at, not data for the application to parse: there is no output schema. (Contrast **[Structured Output](structured-output.md)**, where the return annotation *is* the schema.)
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!!! info
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### Try it
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Drop any PNG next to `server.py`, name it `logo.png`, and run:
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```console
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uv run mcp dev server.py
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```
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Open the **Tools** tab and call `logo`. The result is not a string: it is an `image` content block, and the Inspector renders it as a picture. You returned `bytes`; everything between that and the pixels on screen was the SDK.
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Open the **Tools** tab and call `logo`. The result is not a string: it is an `image` content block, and the Inspector renders your picture. Everything between the file on disk and the pixels on screen was the SDK.
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## Returning audio
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`Audio` is the same shape:
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`Audio` is the same shape. Keep `logo.png` where it was, and put any WAV beside it as `chime.wav`:
Same deal: raw bytes in, base64 and a MIME type out, no output schema.
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Same deal: a file on disk in, base64 and a MIME type out, no output schema.
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## Bytes or a file
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Both helpers also accept `path=` instead of `data=`. The file is read when the result is built, and the MIME type is guessed from the suffix:
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Both helpers also accept `data=` (raw bytes) instead of `path=`. That is the mode for bytes that never came from a file of their own — a database column, an HTTP response, something Pillow just drew:
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```python title="server.py" hl_lines="14 15"
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--8<--"docs_src/media/tutorial003.py"
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```
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With `path=` there is nothing to declare: the file is read when the result is built, and the MIME type is guessed from the suffix:
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An `Icon` is metadata, not content. It doesn't carry the image; it points at one with a URI, and a client may fetch it and show it next to your server's name, a tool, a resource, or a prompt.
*`src` is a URI the client can resolve: `https:`, or a `data:` URI if you want the icon embedded with no extra fetch.
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## Recap
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* Return an `Image` or `Audio` from a tool and the client receives an `ImageContent` / `AudioContent` block: your bytes base64-encoded, with a MIME type.
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* Build one from in-memory `data=`plus an explicit `format=`, or from a `path=`and let the suffix decide.
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* Build one from a `path=`and let the suffix decide the MIME type, or from in-memory `data=`plus an explicit `format=`.
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* Media results carry no `structured_content` and no output schema.
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* An `Icon` is a pointer: a `src` URI plus optional `mime_type`, `sizes`, and `theme`.
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*`icons=[...]` works on the server, on tools, on resources, and on prompts, and clients find them on the matching objects.
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