firstsun-dev Designing with Sleek
Overview
sleek.design is an AI-powered mobile app design tool. You interact with it via a REST API at /api/v1/* to create projects, describe what you want built in plain language, and get back rendered screens. All communication is standard HTTP with bearer token auth.
Base URL: https://sleek.design
Auth: Authorization: Bearer $SLEEK_API_KEY on every /api/v1/* request
Content-Type: application/json (requests and responses)
CORS: Enabled on all /api/v1/* endpoints
Prerequisites: API Key
Create API keys at https://sleek.design/dashboard/api-keys. The full key value is shown only once at creation — store it in the SLEEK_API_KEY environment variable.
Required plan: Pro or higher (API access is gated)
Key scopes
| Scope | What it unlocks |
|---|---|
projects:read |
List / get projects |
projects:write |
Create / delete projects |
components:read |
List components in a project |
chats:read |
Get chat run status |
chats:write |
Send chat messages |
screenshots |
Render component screenshots |
Create a key with only the scopes needed for the task.
Security & Privacy
- Single host: All requests go exclusively to
https://sleek.design. No data is sent to third parties. - HTTPS only: All communication uses HTTPS. The API key is transmitted only in the
Authorizationheader to Sleek endpoints. - Minimal scopes: Create API keys with only the scopes required for the task. Prefer short-lived or revocable keys.
- Image URLs: When using
imageUrlsin chat messages, those URLs are fetched by Sleek's servers. Avoid passing URLs that contain sensitive content.
Quick Reference — All Endpoints
| Method | Path | Scope | Description |
|---|---|---|---|
GET |
/api/v1/projects |
projects:read |
List projects |
POST |
/api/v1/projects |
projects:write |
Create project |
GET |
/api/v1/projects/:id |
projects:read |
Get project |
DELETE |
/api/v1/projects/:id |
projects:write |
Delete project |
GET |
/api/v1/projects/:id/components |
components:read |
List components |
GET |
/api/v1/projects/:id/components/:componentId |
components:read |
Get component |
POST |
/api/v1/projects/:id/chat/messages |
chats:write |
Send chat message |
GET |
/api/v1/projects/:id/chat/runs/:runId |
chats:read |
Poll run status |
POST |
/api/v1/screenshots |
screenshots |
Render screenshot |
All IDs are stable string identifiers.
Endpoints
Projects
List projects
GET /api/v1/projects?limit=50&offset=0
Authorization: Bearer $SLEEK_API_KEY
Response 200:
{
"data": [
{
"id": "proj_abc",
"name": "My App",
"slug": "my-app",
"createdAt": "2026-01-01T00:00:00Z",
"updatedAt": "..."
}
],
"pagination": { "total": 12, "limit": 50, "offset": 0 }
}
Create project
POST /api/v1/projects
Authorization: Bearer $SLEEK_API_KEY
Content-Type: application/json
{ "name": "My New App" }
Response 201 — same shape as a single project.
Get / Delete project
GET /api/v1/projects/:projectId
DELETE /api/v1/projects/:projectId → 204 No Content
Components
List components
GET /api/v1/projects/:projectId/components?limit=50&offset=0
Authorization: Bearer $SLEEK_API_KEY
Both list and get accept an optional inlineIcons query param (default false). When omitted, icons render as <iconify-icon> web components and the HTML pulls in the Iconify script — leave it off by default. Pass ?inlineIcons=true only when the consumer needs self-contained SVGs in the HTML (for example, importing into tools that don't run scripts).
Response 200:
{
"data": [
{
"id": "cmp_xyz",
"name": "Hero Section",
"activeVersion": 3,
"versions": [{ "id": "ver_001", "version": 1, "code": "<!DOCTYPE html>...</html>", "createdAt": "..." }],
"createdAt": "...",
"updatedAt": "..."
}
],
"pagination": { "total": 5, "limit": 50, "offset": 0 }
}
Get component
Fetches a single component by ID. Use this when you need the code for a specific screen (e.g., after a chat run returns a componentId in its operations).
GET /api/v1/projects/:projectId/components/:componentId
Authorization: Bearer $SLEEK_API_KEY
Response 200 — same shape as a single item from the list endpoint:
{
"data": {
"id": "cmp_xyz",
"name": "Hero Section",
"activeVersion": 3,
"versions": [{ "id": "ver_001", "version": 1, "code": "<!DOCTYPE html>...</html>", "createdAt": "..." }],
"createdAt": "...",
"updatedAt": "..."
}
}
Chat — Send Message
This is the core action: describe what you want in message.text and the AI creates or modifies screens.
POST /api/v1/projects/:projectId/chat/messages?wait=false
Authorization: Bearer $SLEEK_API_KEY
Content-Type: application/json
idempotency-key: <optional, max 255 chars>
{
"message": { "text": "Add a pricing section with three tiers" },
"imageUrls": ["https://example.com/ref.png"],
"target": { "screenId": "scr_abc" }
}
| Field | Required | Notes |
|---|---|---|
message.text |
Yes | 1+ chars, trimmed |
imageUrls |
No | HTTPS URLs only; included as visual context |
target.screenId |
No | Edit a specific screen using its screenId (not componentId); omit to let AI decide |
?wait=true/false |
No | Sync wait mode (default: false) |
idempotency-key header |
No | Replay-safe re-sends |
Response — async (default, wait=false)
Status 202 Accepted. result and error are absent until the run reaches a terminal state.
{
"data": {
"runId": "run_111",
"status": "queued",
"statusUrl": "/api/v1/projects/proj_abc/chat/runs/run_111"
}
}
Response — sync (wait=true)
Blocks up to 300 seconds. Returns 200 when completed, 202 if timed out.
{
"data": {
"runId": "run_111",
"status": "completed",
"statusUrl": "...",
"result": {
"assistantText": "I added a pricing section with...",
"operations": [
{ "type": "screen_created", "screenId": "scr_xyz", "screenName": "Pricing", "componentId": "cmp_xyz" },
{ "type": "screen_updated", "screenId": "scr_abc", "componentId": "cmp_abc" },
{ "type": "theme_updated" }
]
}
}
}
Chat — Poll Run Status
Use this after async send to check progress.
GET /api/v1/projects/:projectId/chat/runs/:runId
Authorization: Bearer $SLEEK_API_KEY
Response — same shape as send message data object:
{
"data": {
"runId": "run_111",
"status": "queued",
"statusUrl": "..."
}
}
When completed successfully, result is present:
{
"data": {
"runId": "run_111",
"status": "completed",
"statusUrl": "...",
"result": {
"assistantText": "...",
"operations": [...]
}
}
}
When failed, error is present:
{
"data": {
"runId": "run_111",
"status": "failed",
"statusUrl": "...",
"error": { "code": "execution_failed", "message": "..." }
}
}
Run status lifecycle: queued → running → completed | failed
Screenshots
Takes a snapshot of one or more rendered components.
POST /api/v1/screenshots
Authorization: Bearer $SLEEK_API_KEY
Content-Type: application/json
{
"componentIds": ["cmp_xyz", "cmp_abc"],
"projectId": "proj_abc",
"format": "png",
"scale": 2,
"gap": 40,
"padding": 40,
"background": "transparent"
}
| Field | Default | Notes |
|---|---|---|
format |
png |
png or webp |
scale |
2 |
1–3 (device pixel ratio) |
gap |
40 |
Pixels between components |
padding |
40 |
Uniform padding on all sides |
paddingX |
(optional) | Horizontal padding; overrides padding for left/right when provided |
paddingY |
(optional) | Vertical padding; overrides padding for top/bottom when provided |
paddingTop |
(optional) | Top padding; overrides paddingY when provided |
paddingRight |
(optional) | Right padding; overrides paddingX when provided |
paddingBottom |
(optional) | Bottom padding; overrides paddingY when provided |
paddingLeft |
(optional) | Left padding; overrides paddingX when provided |
background |
transparent |
Any CSS color (hex, named, transparent) |
showDots |
false |
Overlay a subtle dot grid on the background |
radius |
48 |
Squircle corner radius per component in pixels (integer ≥ 0); pass 0 for sharp corners |
componentVersionOverrides |
(optional) | Map of componentId → versions[i].id to render at a pinned version instead of activeVersion (see Pinned versions) |
themeVersionOverrides |
(optional) | Map of themeId → versions[i].id to render with a pinned theme version (see Pinned versions) |
Padding resolves with a cascade: per-side → axis → uniform. For example, paddingTop falls back to paddingY, which falls back to padding. So { "padding": 20, "paddingX": 10, "paddingLeft": 5 } gives top/bottom 20px, right 10px, left 5px.
When showDots is true, a dot pattern is drawn over the background color. The dots automatically adapt to the background: dark backgrounds get light dots, light backgrounds get dark dots. This has no effect when background is "transparent".
Always use "background": "transparent" unless the user explicitly requests a specific background color.
Response: raw binary image/png or image/webp with Content-Disposition: attachment.
Error Shapes
{ "code": "UNAUTHORIZED", "message": "..." }
| HTTP | Code | When |
|---|---|---|
| 401 | UNAUTHORIZED |
Missing/invalid/expired API key |
| 403 | FORBIDDEN |
Valid key, wrong scope or plan |
| 404 | NOT_FOUND |
Resource doesn't exist |
| 400 | BAD_REQUEST |
Validation failure |
| 409 | CONFLICT |
Another run is active for this project |
| 500 | INTERNAL_SERVER_ERROR |
Server error |
Chat run-level errors (inside data.error):
| Code | Meaning |
|---|---|
out_of_credits |
Organization has no credits left |
execution_failed |
AI execution error |
Prompting Sleek
Sleek has its own AI that plans screen content, visual style, and layout. Pass the user's request to Sleek as-is — don't add details the user didn't ask for. If the user described specific screens and styling, include those. If they just said "build me a running app," send that and let Sleek decide the rest. Sleek produces richer designs when given room to plan, so avoid inventing screen content or layout details that the user didn't specify.
Designing
1. Create a project
Create a project with POST /api/v1/projects if one doesn't exist yet. Ask the user for a name, or derive one from the request.
Each project has its own theme, style, and design system. If the user wants multiple design variations, create a separate project for each variation.
2. Send a chat message
Describe what to build using POST /api/v1/projects/:id/chat/messages. You can use the user's words directly — Sleek's AI interprets natural language. You do not need to decompose the request into screens; send the full intent as a single message and let Sleek decide what screens to create.
Chat messages are async by default — you get a runId and poll for completion with GET /api/v1/projects/:id/chat/runs/:runId. You can also use ?wait=true for a blocking call (up to 300s; falls back to polling if it times out with 202).
Polling: start at 2s interval, back off to 5s after 10s, give up after 5 minutes.
Editing a specific screen: use target.screenId to direct changes to the right screen (uses the screen ID from operations, not the component ID).
One run at a time: only one active run is allowed per project. If you get 409 CONFLICT, wait for the current run to complete before sending the next message. Messages to different projects can run in parallel — use async polling (not ?wait=true) when running multiple projects concurrently.
Safe retries: add an idempotency-key header (≤255 chars) to replay-safe re-sends. The server returns the existing run rather than creating a duplicate.
3. Show the results
After every chat run that produces screen_created or screen_updated operations, always take screenshots and show them to the user using POST /api/v1/screenshots. Never silently complete a chat run without delivering the visuals.
- New screens: one screenshot per screen + one combined screenshot of all screens in the project.
- Updated screens: one screenshot per affected screen.
Use background: "transparent" for all screenshots unless the user explicitly requests otherwise.
Save screenshots in the project directory (not a temporary folder) so the user can easily view them.
Implementing Designs
When the user wants to implement the designs in code (not just preview them), always fetch the component HTML code — do not rely on screenshots alone.
Use GET /api/v1/projects/:id/components/:componentId to fetch each screen's code. The componentId comes from the chat run's result.operations.
Which version to use
Each component carries a versions[] array and an activeVersion: number. By default, use the entry where versions[i].version === activeVersion — that's the code currently shown in Sleek.
If the user's prompt pins specific versions, follow those instead (see Pinned versions below).
Pinned versions
The user's prompt may include a pin block telling you to implement specific historical versions instead of the current ones, like this:
... at this exact state instead of the project's current version:
- component cmp_abc: version ver_001
- component cmp_def: version ver_002
- theme thm_ghi: version ver_003
When you see a pin block, implement those exact versions instead of activeVersion. Components not named in the pin block continue to use their active version. Theme IDs surface only inside pin blocks — this skill exposes no separate endpoint to enumerate them.
Fetching the right code
For each pinned component, find the entry in versions[] where versions[i].id matches the given version id (e.g. ver_001) and use its code. Do not fall back to activeVersion for pinned components.
Screenshots of pinned versions
Pass componentVersionOverrides and themeVersionOverrides to POST /api/v1/screenshots:
{
"componentIds": ["cmp_abc"],
"projectId": "proj_xyz",
"componentVersionOverrides": { "cmp_abc": "ver_001" },
"themeVersionOverrides": { "thm_ghi": "ver_003" }
}
Keys are component / theme public ids; values are the corresponding versions[i].id. Entities missing from a map fall back to their active version. Include the override maps whenever the prompt specified pinned versions.
HTML prototypes
The component code is a complete HTML document — save it directly to a .html file. No build step needed.
Native frameworks (React Native, SwiftUI, etc.)
Use both the HTML code and the screenshots together:
- HTML code is the implementation reference — it contains the exact structure, layout, styling, colors, spacing, content, image URLs, and icon names.
- Screenshots are the visual target — use them to verify your implementation matches the intended look.
The HTML tells you how to build it; the screenshot tells you what it should look like.
Icons
Sleek uses Iconify icons in the format prefix:name (e.g., solar:heart-bold, material-symbols:search-rounded, lucide:settings). The most common sets are Solar, Hugeicons, Material Symbols and MDI.
Use the exact icons from the HTML code — do not substitute with a different icon set. Matching icons is important for design fidelity.
When implementing icons:
Check if the project already has an icon system that supports the same sets Sleek uses (Solar, Hugeicons, Material Symbols, MDI). If so, use it. Note:
@expo/vector-iconsdoes not support these sets — do not use it as a substitute.Otherwise, fetch the SVGs from the Iconify API and embed them in the code:
GET https://api.iconify.design/{prefix}/{name}.svgExample:
https://api.iconify.design/solar/heart-bold.svgCollect all icon names from the HTML, fetch their SVGs, and save them as static assets or string constants in the codebase. For React Native / Expo, render them with
react-native-svg'sSvgXmlcomponent — this works in Expo Go with no additional native dependencies.
Fonts
The HTML includes Google Fonts via <link> tags in the <head>. Use the same fonts and weights when implementing in a native framework — extract the font family names and weights from the <link> tags.
Navigation
The designs may include navigation elements like tab bars and headers. Update the project's navigation styling and structure to match the designs — don't just implement the screen content while leaving the default navigation untouched.
Pagination
All list endpoints accept limit (1–100, default 50) and offset (≥0). The response always includes pagination.total so you can page through all results.
GET /api/v1/projects?limit=10&offset=20
Tips
Saving component HTML to files
Component code can be large. When saving it to .html files, avoid writing the content through your text output — this is slow and wastes tokens. Instead, use shell commands to fetch the API response and write it directly to disk (e.g., pipe the response body into a file). This applies to both single and multiple components.
Common Mistakes
| Mistake | Fix |
|---|---|
Sending to /api/v1 without Authorization header |
Add Authorization: Bearer $SLEEK_API_KEY to every request |
| Using wrong scope | Check key's scopes match the endpoint (e.g. chats:write for sending messages) |
| Sending next message before run completes | Poll until completed/failed before next send |
Using wait=true on long generations |
It blocks 300s max; have a fallback to polling for 202 response |
HTTP URLs in imageUrls |
Only HTTPS URLs are accepted |
Assuming result is present on 202 |
result is absent until status is completed |
Using screenId as componentIds in screenshots |
screenId and componentId are different; always use componentId from operations for screenshots |
Confusing versions[i].version (number) with versions[i].id (string) |
When resolving pinned versions, match by id (e.g. ver_001); version is the numeric index |