Sleek Design Mobile Apps

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+ (API access is gated)

Key scopes

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 Authorization header 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 imageUrls in chat messages, those URLs are fetched by Sleek's servers. Avoid passing URLs that contain sensitive content.

Handling high-level requests

When the user says something like "design a fitness tracking app" or "build me a settings screen":

1. Create a project if one doesn't exist yet (ask the user for a name, or derive one from the request)
2. Send a chat message describing what to build — you can use the user's words directly as message.text; Sleek's AI interprets natural language
3. Follow the screenshot delivery rule below to show the result

You do not need to decompose the request into screens first. Send the full intent as a single message and let Sleek decide what screens to create.

Screenshot delivery rule

After every chat run that produces screen_created or screen_updated operations, always take screenshots and show them to the user. Never silently complete a chat run without delivering the visuals.

When screens are created for the first time on a project (i.e. the run includes screen_created operations), deliver:

1. One screenshot per newly created screen (individual componentIds: [screenId])
2. One combined screenshot of all screens in the project (componentIds: [all screen ids])

When only existing screens are updated, deliver one screenshot per affected screen.

Use background: "transparent" for all screenshots unless the user explicitly requests otherwise.

Quick Reference — All Endpoints

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

Response 200:

{
  "data": [
    {
      "id": "cmp_xyz",
      "name": "Hero Section",
      "activeVersion": 3,
      "versions": [{ "id": "ver_001", "version": 1, "createdAt": "..." }],
      "createdAt": "...",
      "updatedAt": "..."
    }
  ],
  "pagination": { "total": 5, "limit": 50, "offset": 0 }
}

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" }
}

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" },
        { "type": "screen_updated", "screenId": "scr_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"
}

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": "..." }

Chat run-level errors (inside data.error):

Flows

Flow 1: Create project and generate a UI (async + polling)

1. POST /api/v1/projects                              → get projectId
2. POST /api/v1/projects/:id/chat/messages            → get runId (202)
3. Poll GET /api/v1/projects/:id/chat/runs/:runId
   until status == "completed" or "failed"
4. Collect screenIds from result.operations
   (screen_created and screen_updated entries)
5. Screenshot each affected screen individually
6. If any screen_created: also screenshot all project screens combined
7. Show all screenshots to the user

Polling recommendation: start at 2s interval, back off to 5s after 10s, give up after 5 minutes.

Flow 2: Sync mode (simple, blocking)

Best for short tasks or when latency is acceptable.

1. POST /api/v1/projects/:id/chat/messages?wait=true
   → blocks up to 300s
   → 200 if completed, 202 if timed out
2. If 202, fall back to Flow 1 polling with the returned runId
3. On completion, screenshot and show affected screens (see screenshot delivery rule)

Flow 3: Edit a specific screen

1. GET /api/v1/projects/:id/components         → find screenId
2. POST /api/v1/projects/:id/chat/messages
   body: { message: { text: "..." }, target: { screenId: "scr_xyz" } }
3. Poll or wait as above
4. Screenshot the updated screen and show it to the user

Flow 4: Idempotent message (safe retries)

Add idempotency-key header on the send request. If the network drops and you retry with the same key, the server returns the existing run rather than creating a duplicate. The key must be ≤255 chars.

POST /api/v1/projects/:id/chat/messages
idempotency-key: my-unique-request-id-abc123

Flow 5: One run at a time (conflict handling)

Only one active run is allowed per project. If you send a message while one is running, you get 409 CONFLICT. Wait for the active run to complete before sending the next message.

409 response → poll existing run → completed → send next message

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

Common Mistakes