Create and refine YouTube thumbnails without leaving the conversation. Give your AI assistant a video title plus 1–3 reference thumbnails whose style you want to match, get a finished thumbnail back in chat, then keep editing it in plain language — "make the text yellow", "swap the background for a city at night".
These are the same generations and edits as the Thumbnail Lab in your NexLev dashboard — same account, same allowance, and everything you make in chat shows up in your Lab history.
Prerequisites
- Connected AI assistant — Claude, ChatGPT, or any other supported platform
- Signed in with your NexLev account (OAuth) — Connect to your AI assistant
- Lite, Pro, or Premium plan — Free plans do not have access. Upgrade your plan to get started.
How It Works
Generate
Give your assistant the video title and 1–3 reference thumbnails whose style you like. It can pull references automatically from NexLev's research tools — for example the thumbnails of outlier videos in your niche via Trending Videos or YouTube Tools.
Optionally add creative direction ("use a red arrow", "dark background"), a short script summary for extra context, or ask for a text-free image.
Tools
generate_thumbnail
Generates a brand-new thumbnail from your video title plus 1–3 reference thumbnails whose style should be matched. Returns a jobId immediately — your assistant then polls get_thumbnail_generation_status until the image is ready.
Best for:
- "Make me a thumbnail for this video title"
- "Match the style of the top videos in my niche"
- "Give me a textless thumbnail I can add my own copy to"
- "Try the same title in a darker, higher-contrast style"
Example prompts:
Generate a thumbnail for my video "I Tried Waking Up at 4AM for 30 Days" — match the style of the top productivity channels
Find the 3 highest-outlier videos in the personal finance niche and use their thumbnails as style references for my video "I Saved $10,000 in 90 Days"
Generate a thumbnail for "The Truth About AI Coding Tools" using a dark background and a red arrow, based on this reference: https://i.ytimg.com/vi/dQw4w9WgXcQ/maxresdefault.jpg
Generate a no-text thumbnail for my video "5 Hidden Gems in Japan" so I can add my own headline later
Use the pro model to generate a thumbnail for "My $50,000 Home Studio Tour"
Parameters:
| Parameter | Type | Description |
|---|---|---|
newVideoTitle | string | Required. Title of the video the thumbnail is for |
referenceThumbnailURLs | string[] | Required. 1–3 HTTPS URLs of reference thumbnails (JPEG/PNG/WEBP/GIF, max 2 MB each) |
referenceThumbnailTitles | string[] | Video titles of the references, in the same order — optional, but improves results |
generationInstructions | string | Creative direction, e.g. "use a red arrow", "dark background" (max 2000 chars) |
newVideoScript | string | Script or summary of the video for extra context |
generationMode | enum | classic (full AI thumbnail with text, default) or no_text (textless image) |
imageModel | enum | pro (highest quality, Pro plan only) or lite (fast). Defaults to the best model your plan allows |
get_thumbnail_generation_status
Checks a generation job and returns the finished image. Your assistant polls this every 5 seconds until the job reports completed or failed.
What it returns:
status—pending,processing,completed, orfailedimageUrl— the finished thumbnail, displayed inline in the chatgenerationId— pass this toedit_thumbnailto refine the result
Example prompts:
Parameters:
| Parameter | Type | Description |
|---|---|---|
jobId | string | Required. The jobId from generate_thumbnail |
edit_thumbnail
Applies an AI edit to a thumbnail — change text, colors, background, or objects — from a plain-language instruction. Returns a jobId; your assistant then polls get_thumbnail_edit_status.
Pass the edit prompt plus exactly one image source:
| Source | When to use it |
|---|---|
documentId | Continue refining the same Lab document — preferred for follow-up edits |
generationId | Edit a completed generate_thumbnail result (a Lab document is opened for it) |
imageUrl | Edit any image by HTTPS URL (JPEG/PNG/WEBP/GIF, max 10 MB — imported into the Lab) |
Example prompts:
Replace the background with a city at night and keep the person as-is
Edit this thumbnail so the headline reads "90 DAYS LATER": https://i.ytimg.com/vi/dQw4w9WgXcQ/maxresdefault.jpg
Show me my recent Lab generations and let's edit the second one — make the colors more saturated
Parameters:
| Parameter | Type | Description |
|---|---|---|
prompt | string | Required. Edit instruction, e.g. "make the text yellow" (max 2000 chars) |
documentId | string | Lab document to keep refining — from a previous edit |
generationId | string | A completed generation to edit — from get_thumbnail_generation_status or list_thumbnail_generations |
imageUrl | string | Arbitrary image to edit by HTTPS URL |
imageModel | enum | pro (Pro plan only) or lite. Defaults to the best model your plan allows |
get_thumbnail_edit_status
Checks an edit job and returns the edited image. Polled every 5 seconds until completed or failed.
What it returns:
status—pending,processing,completed, orfailedimageUrl— the edited thumbnail, displayed inline in the chatdocumentId— pass it back toedit_thumbnailto keep refining the same thumbnail
Example prompt:
Parameters:
| Parameter | Type | Description |
|---|---|---|
jobId | string | Required. The jobId from edit_thumbnail |
list_thumbnail_generations
Lists your past Thumbnail Lab generations, newest first, with their status, image URL, and generationId — so you can revisit an earlier thumbnail or pick one up for editing.
Best for:
- "Show me the thumbnails I made this week"
- "Find the one I generated for my morning routine video and edit it"
Example prompts:
List my recent generations and edit the newest one — make the text yellow
Parameters:
| Parameter | Type | Description |
|---|---|---|
limit | number | Results per page — 1–50, default 10 |
page | number | Page number, default 1 (newest first) |
Image Models
| Model | Description | Available on |
|---|---|---|
pro | Highest quality | Pro plan |
lite | Fast | All Lab plans |
If you don't pick a model, you automatically get the best one your plan allows.
Example Workflows
Niche-matched thumbnail from scratch
Find the 3 highest-outlier videos in the "AI tools" niche from the last 30 days, then generate a thumbnail for my video "I Replaced My Whole Workflow With AI" in their style
Your assistant finds the outlier videos, reuses their thumbnails as references, generates, polls, and shows you the result.
Iterate to a final cut
Generate a thumbnail for "The Only Budget Video You Need" based on these two references, then make the text yellow, then swap the background for a plain dark gradient
Each round is a separate edit on the same Lab document — you keep every intermediate version.
Rework an existing thumbnail
Take the thumbnail from this video and change the headline to "IT GOT WORSE": https://www.youtube.com/watch?v=dQw4w9WgXcQ
A/B variants for one title
Generate two thumbnails for "I Quit My Job After 9 Years" — one with a dark high-contrast style and one bright and colorful
Included Allowance
One shared allowance across chat and the dashboard — a generation from your AI assistant counts exactly the same as one made in the web Lab.
| Plan | Generations | AI edits |
|---|---|---|
| Free | — (not available) | — (not available) |
| Lite | 3 / day · 10 / month | 3 / day · 15 / month |
| Pro | 5 / day · 25 / month | 5 / day · 25 / month |
Beyond Your Allowance (pay as you go)
With usage credits enabled in your NexLev account you can keep working after your included allowance runs out. Extra actions are billed from your credit balance:
| Action | Lite model | Pro model |
|---|---|---|
| Generation | $0.15 | $0.40 |
| AI edit | $0.10 | $0.25 |
- You're always told the price before an over-allowance action is charged.
- Failed jobs are refunded automatically — you only pay for thumbnails that actually complete.
- Pay-as-you-go usage is capped at 30 generations and 30 edits per rolling hour.
Without usage credits enabled, the tools simply stop at your included allowance and tell you when it resets.
Troubleshooting
"This tool requires an OAuth connection"
- Thumbnail Lab is unavailable on API-key connections. Reconnect your assistant with a NexLev account sign-in — see the Quickstart.
Reference thumbnail rejected
- References must be HTTPS URLs pointing at a JPEG, PNG, WEBP, or GIF under 2 MB. If a
maxresdefault.jpgURL 404s, that video has no max-res thumbnail — tryhqdefault.jpginstead. - You need at least 1 and at most 3 references.
Job stuck on processing
- Generations and edits normally finish in 30–90 seconds. Your assistant polls for up to 5 minutes; if it times out, ask it to check the status again with the same
jobId.
Job failed
- Failed jobs are refunded automatically — no allowance or credits are consumed. Try again, and simplify very long
generationInstructionsif it keeps failing.
pro model rejected
- The
proimage model is Pro-plan only. OmitimageModeland you'll get the best model your plan allows.
Edited image is missing my manual layers
- Expected. AI edits act on the base image; layers you added in the web editor are preserved in the Lab but not baked into the image returned in chat.
Allowance reached
- Enable usage credits in your NexLev account to keep going past your included allowance, or wait for the reset your assistant reports. Upgrade to Pro for a larger included allowance.
What's Next?
- Trending Videos — Find the outlier videos whose thumbnails make the best style references
- Similar Thumbnails — Search thumbnails visually across millions of YouTube videos
- Swipefile — Save the thumbnails and videos you want to model
- Channel Analytics — Study the channels behind the styles you're matching
- Niche Overview — Understand the audience you're designing for