Adding an image to a text-only request is not just a matter of replacing a string with an array. First decide whether the image is suitable to send; then build the message; finally check what the deployed route actually does with it.
For developers adapting a DeepSeek V4.1 Flash Chat Completions workflow, Mia Maren’s September 16 guide supplies a useful preflight checklist. This walkthrough uses that guide’s vision section and image-validation FAQ—not independently measured endpoint behavior. Its reported upstream limits are checks to verify on your chosen route, not a guarantee of passthrough.
1. Validate the image before constructing the request
Assume you already have a working text-only request and know which provider route you intend to use. For the first image test, choose a small, non-sensitive image whose contents you can check yourself.
Work through these checks in order:
| Check | What to establish before proceeding |
|---|---|
| Actual format | Inspect the real file signature rather than treating a .png filename as proof of PNG content. The guide lists JPEG, PNG, GIF and WebP. |
| Byte size and delivery mode | Measure the image and distinguish inline delivery from file-based delivery. The guide reports upstream limits of 32 MiB per inline image and 64 MiB per file-based image. |
| URL accessibility | If sending an external URL, establish that it is accessible for the intended request. Do not treat being able to open it in your own browser as the final route test. |
| Message role | Use the user-message path shown below. The guide places images in user or developer messages, not system or assistant messages. |
The size figures need a boundary check in the current route documentation. This source does not establish how encoding overhead is counted, and “64 MiB per file” should not be reinterpreted as a blanket allowance for any image URL or entire request. Keep the first test comfortably small instead of starting at a reported maximum.
If a preflight check fails, resolve it before changing the prompt. A more detailed question is not a substitute for a validated input.
2. Change the message structure, not just the text
The guide’s example puts the instruction and image reference inside one user message. Here is the relevant message fragment, adapted for a simple inspection task:
{
"role": "user",
"content": [
{
"type": "text",
"text": "Describe the main visible elements in this image."
},
{
"type": "image_url",
"image_url": {
"url": "https://example.com/test-image.png"
}
}
]
}
The text part states the task; the image_url part supplies the image reference. Notice that content is now an array and the URL is nested inside image_url.
Replace the placeholder URL with your validated test image. This is not a complete request: it omits client configuration, the route’s model identifier and the outer messages array. It also does not demonstrate inline encoding or file upload. Those branches still need their own route-specific documentation and checks.
3. Test the route before calling the migration complete
The guide explicitly calls for checking image size, accessibility, preprocessing, token use and latency on the deployed route. My suggested progression is:
- Establish one positive case. Send the small known image with a question about an observable detail. Record whether the request is accepted and whether the answer matches that detail. Acceptance alone is not evidence of correct visual understanding.
- Isolate failure cases. In a controlled test, separately exercise an inaccessible URL, an unsupported message role and the documented size boundaries. Record the actual rejection or behavior rather than assuming a particular error code.
- Check representative inputs. Try the screenshots or documents the application will use. Record preprocessing choices, correctness, reported token usage and latency before expanding the workload.
These are proposed tests, not results. The useful stopping rule is simple: valid local input permits a route test; only observed route behavior supports a deployment decision. A familiar Chat Completions shape and an illustrative vision payload do not, by themselves, establish a working image integration.