curl -X POST https://eachsense-agent.core.eachlabs.run/v1/chat/completions \
  -H "Content-Type: application/json" \
  -H "X-API-Key: $EACHLABS_API_KEY" \
  -d '{
    "messages": [
      {
        "role": "user",
        "content": "Create a YouTube thumbnail for a tech review video. Split composition with a glowing smartphone on the left and an explosion of colorful app icons on the right, dark background, dramatic lighting, bold and vibrant, 16:9 aspect ratio."
      }
    ],
    "stream": false
  }'

Using Python (OpenAI SDK)

from openai import OpenAI

client = OpenAI(
    api_key="YOUR_EACHLABS_API_KEY",
    base_url="https://eachsense-agent.core.eachlabs.run/v1"
)

response = client.chat.completions.create(
    model="eachsense/beta",
    messages=[{
        "role": "user",
        "content": "Create a YouTube thumbnail for a tech review video. Split composition with a glowing smartphone on the left and an explosion of colorful app icons on the right, dark background, dramatic lighting, bold and vibrant, 16:9 aspect ratio."
    }]
)

print(response.choices[0].message.content)

With Reference Image

Provide a frame from your video or a style reference for consistent channel branding:

curl -X POST https://eachsense-agent.core.eachlabs.run/v1/chat/completions \
  -H "Content-Type: application/json" \
  -H "X-API-Key: $EACHLABS_API_KEY" \
  -d '{
    "messages": [
      {
        "role": "user",
        "content": [
              {"type": "text", "text": "Create a YouTube thumbnail using this video frame as a base. Add dramatic lighting, increase contrast, make the background darker and more cinematic, 16:9 aspect ratio."},
              {"type": "image_url", "image_url": {"url": "https://example.com/video-frame.jpg"}}
            ]
          }
    ],
    "stream": false
  }'

Images are sent inside messages using the OpenAI multimodal content format. Maximum 4 images per request.

Streaming

Set "stream": true for real-time SSE responses, or "stream": false for complete result in a single response. Streaming is useful for showing progress in UIs; non-streaming is simpler for scripts and automation.

Thumbnail Anatomy

Element	Purpose	Tip
Subject	Primary focal point	Place on the left or right third
Background	Sets mood and context	Dark backgrounds increase contrast
Color contrast	Draws the eye	Use complementary colors
Negative space	Area for text overlay	Reserve 30% for title text
Emotion	Creates connection	Dramatic expressions or reactions

Prompt Engineering Tips

Keywords That Work

YouTube thumbnail, dramatic lighting, bold contrast, vibrant saturated colors,
cinematic composition, dark background, eye-catching, 16:9 aspect ratio,
high impact visual, attention-grabbing, split composition, spotlight effect

Keywords to Avoid

subtle and muted — thumbnails need to pop at small sizes
lots of small details — lost in YouTube's grid view
text-heavy — add text in post-production for reliability
realistic documentary style — too bland for thumbnail grid

Prompt Structure

YouTube thumbnail for [topic], [subject description], [background/lighting], [color scheme], [composition notes], 16:9 aspect ratio

Examples

Cooking Channel Thumbnail

curl -X POST https://eachsense-agent.core.eachlabs.run/v1/chat/completions \
  -H "Content-Type: application/json" \
  -H "X-API-Key: $EACHLABS_API_KEY" \
  -d '{
    "messages": [
      {
        "role": "user",
        "content": "Create a YouTube thumbnail for a cooking video. A perfectly plated gourmet burger with melting cheese and steam rising, dramatic dark background with warm spotlight, ultra close-up food photography style, vibrant colors, 16:9."
      }
    ],
    "stream": false
  }'

Science Explainer Thumbnail

curl -X POST https://eachsense-agent.core.eachlabs.run/v1/chat/completions \
  -H "Content-Type: application/json" \
  -H "X-API-Key: $EACHLABS_API_KEY" \
  -d '{
    "messages": [
      {
        "role": "user",
        "content": "Design a YouTube thumbnail for a space science video. A massive black hole warping light around it, stars streaking into the event horizon, deep blue and purple cosmic colors, dramatic and awe-inspiring, cinematic 16:9 aspect ratio."
      }
    ],
    "stream": false
  }'

Before/After Transformation Thumbnail

curl -X POST https://eachsense-agent.core.eachlabs.run/v1/chat/completions \
  -H "Content-Type: application/json" \
  -H "X-API-Key: $EACHLABS_API_KEY" \
  -d '{
    "messages": [
      {
        "role": "user",
        "content": "Create a YouTube thumbnail showing a dramatic room makeover. Split down the middle: left side is a dull, cluttered room in desaturated tones, right side is the same room transformed into a stylish modern space with warm lighting and vibrant colors, 16:9."
      }
    ],
    "stream": false
  }'

Click-Through Rate Tips

Face close-ups with exaggerated expressions consistently outperform other thumbnail styles
3 or fewer elements — thumbnails are viewed at ~120px wide on mobile
High contrast between subject and background is critical
Bright yellow, red, and orange accents draw attention in YouTube's white feed
Consistency — use a recognizable style across your channel for brand recall

Workflow

# Step 1: Generate the base thumbnail concept
curl -X POST https://eachsense-agent.core.eachlabs.run/v1/chat/completions \
  -H "Content-Type: application/json" \
  -H "X-API-Key: $EACHLABS_API_KEY" \
  -d '{
    "messages": [
      {
        "role": "user",
        "content": "YouTube thumbnail for a fitness transformation video. Athletic person mid-action with dynamic pose, bold red and black background, dramatic gym lighting, powerful and motivating, 16:9."
      }
    ],
    "stream": false
  }'

# Step 2: Refine with more specifics
curl -X POST https://eachsense-agent.core.eachlabs.run/v1/chat/completions \
  -H "Content-Type: application/json" \
  -H "X-API-Key: $EACHLABS_API_KEY" \
  -d '{
    "messages": [
      {
        "role": "user",
        "content": "YouTube thumbnail for a fitness transformation video. Athletic person mid-action with dynamic pose, bold red and black background, dramatic gym lighting, powerful and motivating, 16:9."
      },
      {
        "role": "assistant",
        "content": "..."
      },
      {
        "role": "user",
        "content": "Add more dramatic backlighting creating a silhouette edge glow effect. Make the reds more saturated and add subtle smoke in the background."
      }
    ],
    "stream": false
  }'

youtube-thumbnail

YouTube Thumbnail Design

Quick Start

Using curl