> ## 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
> Write clear Lucy 2.6 video-editing prompts, choose commands, and control edit scope.
Lucy 2.6 edits video from a written instruction and an optional reference image. Describe the visible change, identify the edit target, and make the edit scope clear.
> [!TIP]
>
> [Prompt enhancement](https://docs.platform.decart.ai/models/realtime/streaming-best-practices.md#use-prompt-enhancement) (`enhance: true`) rewrites your instruction to fit the input video and any reference image. Prompt enhancement is on by default and recommended for best results.
> [!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.
## Basics
Three inputs shape the result:
* **Input video:** The subject, objects, and scene Lucy can see.
* **Reference image:** The appearance you want to apply.
* **Prompt:** What should change and where the change belongs.
### Write a clear edit
Describe what should visibly change in the video. Name the edit target and what you want it to look like, rather than relying on mood or abstract ideas alone.
A **command** names the type of edit, such as **Swap**, **Add**, or **Replace**. Start with the command, then name the edit target and the change you want. Natural language works too: prompt enhancement adapts your instruction to the video and any reference image.
Example:
Copy
`**Swap** only my shirt for the yellow bomber jacket.`
Include the details that define the edit, such as color, material, quantity, placement, or layering. Describe visible behavior when it matters, such as a bird perching on your shoulder. Avoid asking for a sequence of actions or a reaction at a specific moment, such as the bird taking off whenever you speak.
Start with a clear edit, then try combining related changes. For example, change your outfit and the scene around you together. [Learn more about compound prompts below](#combine-edits).
### Choose a clear input
Keep the edit target (the person, object, or area you want to change) visible, well lit, and distinguishable from similar objects. Start with steady framing, moderate movement, and consistent focus.
Identify edit targets by visible details, such as “the person wearing the red shirt” or “the striped bag on the chair.”
> [!WARNING]
>
> Lucy edits your live video in real time. Name the edit target explicitly in your prompt. For best results, make sure it is visible at the moment the prompt is sent.
### Use reference images deliberately
A reference supplies appearance details for your edit. Your prompt identifies what to use and where it belongs.
* Use a sharp image that clearly shows the item or scene you want to use.
* Make sure important details are visible and easy to distinguish from nearby objects.
* Name the item, character, scene, or style to use, especially when the reference contains several elements.
* Include colors, materials, shapes, or patterns that matter to the edit.
* Describe only the reference details you want to apply. Include its scene when changing the background.
> [!WARNING]
>
> Include a prompt with your reference image to specify the intended edit.
## Prompt templates and examples
Each template starts with a **command**, shown in bold, followed by placeholders for the edit target and the requested change. Replace the placeholders with your own details. The command words are also bolded in the example prompts.
Each example below begins with the unedited input video, with the prompt template below it. Select an example tab beneath the video to see the edited result and its user prompt. Examples that use a reference also show that image.
### Substitute
Replace a person or animal in the video with a different person, animal, or character. Use [Swap](#swap) to change clothing while keeping the same person.
**Original person**
**Aquatic dragon**
**Robot ballerina**
**Racing driver**
**Original person**
Template:
Copy
`**Substitute** with .`
**Aquatic dragon**
Prompt:
Copy
`**Substitute** the woman with the aquatic dragon.`
`**Substitute** the woman with the blue-haired racing driver.`
Reference
**Tips**
* Describe the character you want, including any defining attire or features.
* Choose a reference that clearly shows the replacement character’s design.
| ✅ Do | ❌ Don't |
| - | - |
| `Substitute me with the blue-haired racing driver.` | Request only a face replacement when you want to replace the person. |
### Add
Introduce a new object, creature, or visual effect into the scene. Name the addition and where it belongs.
**Original selfie**
**Smiley bucket hat**
**Chameleon**
**Gold chains**
**Original selfie**
Template:
Copy
`**Add** to .`
**Smiley bucket hat**
Prompt:
Copy
`**Add** the blue bucket hat to his head.`
Reference
**Chameleon**
Prompt:
Copy
`**Add** this chameleon crawling across my shoulders and behind my head.`
`**Add** the oversized gold chains around his neck.`
Reference
**Tips**
* Say how many items or creatures to add when the number matters.
* Use a reference image to show a particular object or creature design.
| ✅ Do | ❌ Don't |
| - | - |
| Name where an added object or creature belongs, such as a chameleon on your shoulder. | Provide a reference without specifying where the addition belongs in your video. |
| Describe how the addition sits on or attaches to the subject, such as a hat resting on your head or a necklace hanging around your neck. | Ask an added creature to react at specific moments, such as a chameleon changing direction whenever you speak. |
| Place an added creature on a visible person, as in the shoulder chameleon example. | Add people or animals in the background and ask them to act on their own. |
### Swap
Change a person’s clothes or costume while keeping their visual identity. To replace the entire person with a character, see [Substitute](#substitute).
**Original outfit**
**Vermilion couture gown**
**Sashiko jacket**
**Sculptural pleats**
**Original outfit**
Template:
Copy
`**Swap** her outfit for the yellow shirt and teal pleated trousers.`
Reference
**Tips**
* Name one garment, several specific items, or the complete outfit so the scope is clear.
* Use a reference where the requested garments are easy to distinguish from accessories and neighboring clothing.
| ✅ Do | ❌ Don't |
| - | - |
| Use Swap when it’s important to preserve a person’s visual identity. | Use Substitute for a clothing-only change when the person should remain recognizable. |
| Name the full outfit when you want all its pieces: `Swap my outfit for the tuxedo.` | Name only one garment when you want the full outfit: `Dress me in the jacket.` leaves out the tuxedo trousers. |
### Set the background
Replace the scene around the subject while keeping their appearance, clothing, and anything they are holding. To change the appearance of both the subject and the scene, see [Restyle](#restyle).
**Original background**
**Megacity edge**
**Coastal sunset**
**Tropical ruins**
**Original background**
Template:
Copy
`**Set the background** to .`
**Megacity edge**
Prompt:
Copy
`**Set the background** to the exposed edge of a skyscraper high above a dense megacity on a partly cloudy day.`
**Coastal sunset**
Prompt:
Copy
`**Set the background** to a coastal cliff at vivid sunset, with powerful waves crashing against the rocks below.`
**Tropical ruins**
Prompt:
Copy
`**Set the background** to this tropical forest with ancient stone ruins, colorful flowers and a waterfall near the center.`
Reference
**Tips**
* Describe a complete scene with the details that define it: layout, landmarks, weather, or time of day.
* Use a reference image when you need more realism or a location that's very specific or hard to describe accurately.
* Keep the request focused on the scene.
* A background reference guides the scene’s appearance. Its layout may change to fit your video’s framing and camera angle.
| ✅ Do | ❌ Don't |
| - | - |
| `Set the background to a sunny beach.` | `Restyle the whole scene as a sunny beach.` when you want to replace only the background and retain the person’s appearance. |
### Replace
Exchange an existing object in the scene for another. Identify the existing object and the replacement.
**Original scene**
**Aperitif bottle**
**Gold and ruby**
**Lit candelabra**
**Original scene**
Template:
Copy
`**Replace** with .`
**Aperitif bottle**
Prompt:
Copy
`**Replace** the wine bottle in my hand with this aperitif bottle.`
Reference
**Gold and ruby**
Prompt:
Copy
`**Replace** my earrings with compact gold-and-ruby drops about half the length of my ears.`
Reference
**Lit candelabra**
Prompt:
Copy
`**Replace** the lamp and its wire with this blue candelabra with burning flames.`
Reference
**Tips**
* Identify the existing object by its holder, color, location, or another distinguishing feature.
* For held objects, choose a replacement that fits the visible grip and action, including its scale and orientation.
* A broad object can hide fingers that a narrower replacement would expose.
| ✅ Do | ❌ Don't |
| - | - |
| Identify the object by its holder, color, or location when several objects could match. | Say “the bottle” when several bottles are visible. |
| For a held-object replacement, choose a source where the grip is visible and fits the new object. | Use a broad object that hides the grip needed for a much narrower replacement. |
### Remove
Remove an object from the scene.
**Original presenter**
**Remove mic**
**Remove mug**
**Remove denim shirt**
**Original presenter**
Template:
Copy
`**Remove**
**Remove mic**
Prompt:
Copy
`**Remove** the microphone, its stand, and the entire connected cable from the table.`
**Remove mug**
Prompt:
Copy
`**Remove** the yellow mug from the table.`
**Remove denim shirt**
Prompt:
Copy
`**Remove** the denim shirt, leaving his gray T-shirt.`
**Tips**
* Name any connected parts you also want to remove, such as a microphone’s stand and cable.
* Describe the intended visible area after removal when that helps clarify the result.
| ✅ Do | ❌ Don't |
| - | - |
| `Remove the microphone, its stand, and the connected cable from the table.` | Name only the microphone when you also want its stand and cable removed. |
### Change attribute
Change a person’s features or a property of another element in the scene, such as hair color, surface finish, or pattern. Name the edit target and the attribute you want to change.
**Original guitar**
**Vivid orange**
**Polished gold**
**Magenta jelly**
**Original guitar**
Template:
Copy
`**Change** the of
**Vivid orange**
Prompt:
Copy
`Make the body of my guitar vivid orange.`
**Polished gold**
Prompt:
Copy
`Give the body of my guitar a polished gold finish.`
**Magenta jelly**
Prompt:
Copy
`Make the body of my guitar transparent magenta jelly.`
**Tips**
* Name the edit target, the attribute, and the desired appearance. Use natural wording, such as “make my hair blue” or “make the body of my guitar orange.”
* Use color, material, and pattern descriptions to explore different appearances of the same edit target.
| ✅ Do | ❌ Don't |
| - | - |
| `Make my jacket’s sleeves blue.` | `Make my jacket blue.` when you want only the sleeves to change color. |
### Restyle
Change the entire scene’s visual style or turn it into a different kind of world, transforming both the subject and the environment. To replace the background while keeping the subject, see [Set the background](#set-the-background).
**Original scene**
**Comic Mars**
**Mushroom land**
**Ice and snow**
**Original scene**
Template:
Copy