> ## Documentation Index
> Fetch the complete documentation index at: https://docs.platform.decart.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Prompting Guide

> How to write effective prompts for VTON 3.5 — principles, examples, and common mistakes for every try-on.

VTON 3.5 applies garments and accessories from a reference image onto a person. A strong prompt tells the model what item or outfit to apply, where it belongs, and which visible garment details matter.

Write the prompt like clear styling direction: name the item, describe what it looks like, and avoid asking for unrelated changes.

<Note>
  **Prompt length.** Prompts have a maximum length. As a rough estimate, about 750 characters of English (around 120 words) fit. The exact limit depends on the wording, and other languages may allow fewer characters. If your prompt is too long, you get an error that tells you how many characters of it fit. This applies whether or not prompt enhancement is on.
</Note>

## At a glance

| ✅ Do                                                                                                                              | ❌ Don't                                                                          |
| --------------------------------------------------------------------------------------------------------------------------------- | -------------------------------------------------------------------------------- |
| `"Substitute the upper body garment with a grey sleeveless crew-neck t-shirt featuring a single chest pocket with a small logo."` | `"Make me fashionable."` — too vague                                             |
| `"Substitute the footwear with white low-top leather sneakers with a clean toe box and thin rubber sole."`                        | `"Change the background."` — unrelated change                                    |
| `"Add a black thick ribbed-knit beanie with a folded cuff and a small white brand label to the outfit."`                          | `"Add the [Brand name] logo."` — inventing a detail not visible in the reference |

## Core prompting principles

### 1. Use one clear action

Each prompt should focus on one try-on action.

Use **substitute** when an existing clothing region should be replaced:

* “**Substitute** the upper body garment with a cropped black leather jacket.”
* “**Substitute** the lower body garment with wide-leg white tailored trousers.”
* “**Substitute** the outfit with a red sleeveless midi dress.”

Use **add** when the item sits on top of the existing outfit and does not replace clothing:

* “**Add** a black ribbed-knit beanie to the outfit.”
* “**Add** a tan leather shoulder bag to the outfit.”
* “**Add** a gold pendant necklace to the outfit.”

Avoid mixing actions in one prompt, such as replacing a jacket and adding a bag at the same time.

### 2. Name the region being changed

Be specific about what part of the outfit should change.

| Region to change                                    | Start the prompt with                                     |
| --------------------------------------------------- | --------------------------------------------------------- |
| Tops, jackets, coats, hoodies, shirts, and sweaters | `"Substitute the upper body garment with <description>."` |
| Pants, skirts, shorts, and other bottoms            | `"Substitute the lower body garment with <description>."` |
| Dresses, jumpsuits, matching sets, or full looks    | `"Substitute the outfit with <description>."`             |
| Shoes                                               | `"Substitute the footwear with <description>."`           |
| Hats                                                | `"Substitute the hat with <description>."`                |
| Necklaces                                           | `"Substitute the necklace with <description>."`           |
| Accessories to add on top                           | `"Add <description> to the outfit."`                      |

### 3. Let the reference image lead

<Note>
  The reference image is the source of truth for the garment. Describe what it actually shows, explicitly — not a new imagined version of it.
</Note>

Good prompts describe the visible item directly:

* “Substitute the upper body garment with **a dark green hooded jacket**.”
* “Substitute the lower body garment with **white tailored trousers**.”
* “Add **a black ribbed beanie with a folded cuff** to the outfit.”

Avoid relying on vague phrases:

* “Use this.”
* “Make it stylish.”
* “Give me the same vibe.”

### 4. Describe visible garment details

VTON works best when the prompt includes concrete fashion details. Describe what can actually be seen.

Useful details include:

* Color
* Fabric or material
* Garment type
* Fit or silhouette
* Length
* Sleeves
* Neckline or collar
* Closures, such as zipper, buttons, snaps, or drawstrings
* Pockets
* Texture
* Pattern
* Visible logo, graphic, or brand text

Examples:

* “Substitute the upper body garment with **a dark green hooded jacket, zipped closed, with large front utility pockets and a small white logo on the left chest**.”
* “Substitute the lower body garment with **oversized burnt orange sherpa fleece trousers with a drawstring waistband**.”
* “Add **a black thick ribbed-knit beanie with a folded cuff and a small white brand label** to the outfit.”

<Warning>
  Do not invent logos, text, or details that are not visible in the reference image.
</Warning>

### 5. Say whether garments are open or closed

For garments with buttons, zippers, or front openings, include how they are worn.

This matters for:

* Jackets
* Coats
* Cardigans
* Blazers
* Vests
* Dress shirts
* Zip hoodies
* Button-up garments

Examples:

* “Substitute the upper body garment with a black blazer, **worn open on top of a white crew-neck t-shirt**.”
* “Substitute the upper body garment with a navy zip-up hoodie, **zipped closed**.”
* “Substitute the outfit with a **closed** two-button black blazer, a black ribbed turtleneck sweater, and white tailored trousers.”

If the garment is open over another visible layer, describe the base layer too.

## Strong prompt examples

* “Substitute the upper body garment with a grey sleeveless crew-neck t-shirt featuring a single chest pocket with a small logo.”
* “Substitute the outfit with a closed two-button black blazer, a black ribbed turtleneck sweater, and white tailored trousers.”
* “Substitute the lower body garment with oversized wide-leg burnt orange sherpa fleece trousers featuring a drawstring waistband.”
* “Substitute the footwear with white low-top leather sneakers with a clean toe box and thin rubber sole.”
* “Add a black thick ribbed-knit beanie with a folded cuff and a small white brand label to the outfit.”

## Common mistakes

**Being too vague:**

* “Make me fashionable.”
* “Use the reference.”
* “Try this look.”

**Requesting unrelated changes:**

* “Change my face.”
* “Make me taller.”
* “Change the background.”

**Inventing details:**

* “Add the \[Brand name] logo,” unless the logo is clearly visible.
* “Make it silk,” if the reference does not show silk.

<Tip>
  The best VTON prompts are short, visual, and specific: one action, one target region, and a faithful description of the visible garment.
</Tip>

## Writing prompts with an AI assistant

If you would rather not write the prompt yourself, a chat assistant such as ChatGPT, Claude, or Gemini can turn a garment photo into a ready-to-use prompt.

<Steps>
  <Step title="Upload the garment image">
    Open the assistant and upload the garment image (a screenshot from a store page works too).
  </Step>

  <Step title="Add a photo of the person (optional)">
    Also upload a photo of the person who will wear it — this helps the assistant name the region correctly (for example, "the upper body garment").
  </Step>

  <Step title="Paste an instruction and copy the result">
    Paste an instruction like the one below, then copy the result into VTON 3.5.

    ```text Prompt to paste wrap theme={null}
    Look at the attached garment image and write a single virtual try-on prompt. Start it with "Substitute the upper body garment with…" (or "Add … to the outfit" for accessories). Describe only what is visible: color, fabric, garment type, fit, length, sleeves, neckline, closures, pockets, texture, pattern, and any visible logo. Do not invent details that are not shown. Keep it to one sentence.
    ```
  </Step>
</Steps>

Always review the result before using it — check that every detail actually appears in the image, and delete anything the assistant guessed.

## Preparing a clean garment image

VTON 3.5 works best from a clean garment image: just the item, on a plain background, with no one wearing it. Photos from fashion websites usually show a model, a background, and props instead.

You can create a clean version with an image-generating assistant (for example, ChatGPT, Gemini, or another image tool):

<Steps>
  <Step title="Upload the original photo">
    Add the source photo to the assistant.
  </Step>

  <Step title="Ask the tool to isolate the garment">
    Ask the tool to isolate the garment on a plain background, for example:

    ```text Prompt to paste wrap theme={null}
    Extract just the [garment, e.g. green hooded jacket] from this photo and place it on a plain white background. Keep the garment's exact color, shape, and details. Remove the person, the background, and any props.
    ```
  </Step>

  <Step title="Use the cleaned image in VTON 3.5">
    Use the cleaned image as your reference, paired with a descriptive prompt.
  </Step>
</Steps>

Keep the garment's real color and details — do not let the tool restyle or "improve" the item, because VTON reproduces what the reference shows.