Pumbline for VS Code
Validate the JSON schemas you hand to OpenAI, Anthropic and Gemini, diff prompt versions, and see what a prompt costs in tokens and dollars, without leaving the editor.
The eight tools from pumblinedev.com run inside VS Code. They're free and need no account. Your files and selections stay on your machine.
Install
From the Marketplace: open the Extensions view (Ctrl+Shift+X / Cmd+Shift+X), search for Pumbline and click Install. You can also run:
code --install-extension Pumbline.pumbline
From a .vsix file: in the Extensions view, open the … menu, choose Install from VSIX… and pick the file. On the command line:
code --install-extension pumbline-0.1.1.vsix
It works in VS Code 1.90 and later, and in editors built on it such as Cursor, VSCodium and Windsurf.
Where to find it
- Sidebar: click the
{ icon in the Activity Bar. You get every tool, your plan, and a live token count and cost for the file or selection you're working on.
- Command Palette: type
Pumbline: to see every command.
- Right-click: a Pumbline submenu in the editor and in the Explorer. In the Explorer, select two files to diff them.
- Status bar: shows your plan (Free, Pro, or how many trial days are left). Click it to open the account menu.
All eight run locally. Nothing is uploaded.
| Tool |
What it does |
| Schema Validator |
Checks a function or tool definition against OpenAI function calling and structured outputs, Anthropic tool use, or Gemini function declarations. Each problem goes into the Problems panel on the key it's about, with a plain-English fix. Broken JSON (trailing commas, single quotes, comments) can be repaired in one click. The format is detected for you, or you can pin it in settings. |
| Prompt Diff |
Before and after, side by side, by word or by line. Shows the token delta and what it adds per 1,000 calls on the model you pick. Load either side from the active editor, a file, or two files selected in the Explorer. |
| Token Counter |
Counts tokens in the selection or file. Counts are exact for OpenAI models (o200k_base) and clearly marked as estimates for Claude and Gemini, whose tokenizers aren't public. |
| API Cost Calculator |
Ranks every model by price for the text you have open, cheapest first. Set output tokens and calls per month to get a monthly figure. |
| Context Window Visualizer |
Stack your system prompt, history, tool definitions and retrieved chunks against a model's window. Add the active file as a segment and see what fits, what's left and how many more turns you have. |
| JSON Formatter |
Format, sort keys, or minify the selection or the whole file. Invalid JSON is located to the line and column. |
| Base64 Encode / Decode |
Converts the selection in place. Handles UTF-8 correctly and has a URL-safe variant. Works on several selections at once. |
| UUID Generator |
Inserts a fresh ID at every cursor: UUID v4, time-ordered v7, nanoid, or an 8-character short ID. |
Pro
Pro is your pumblinedev.com plan. There's no separate subscription for the editor. Sign in with the same account you use on the website, and if it has Pro, Pro unlocks here too.
| Feature |
What it does |
| Format Converter |
Turns an OpenAI tool definition into an Anthropic or Gemini one, or the other way round. The result opens in a new tab, with notes on anything the target format can't express. |
| Batch Validation |
Checks many test inputs against one schema in a single pass: a folder of JSON files, a JSON array, or a JSONL file. Each failure is reported on the line it's about. |
| History Sync |
Save schemas and prompt diffs from the editor, and open anything you saved on the website. It's the same history in both places. |
7-day free trial. New accounts can start Pro with a 7-day free trial. You add a payment method at checkout and you're charged nothing until the trial ends. Cancel from Billing before then and you pay nothing.
Pro is $9 a month or $84 a year. Prices and what's included are on the pricing page.
Pro tools send the schema or inputs you run them on to pumblinedev.com over HTTPS, because that's where they run. Nothing is kept unless you save it to your history.
Signing in
- Run Pumbline: Sign In, or click Sign in in the sidebar.
- Your browser opens pumblinedev.com. Sign in if you need to, then click Connect.
- The browser hands you back to the editor, and your plan appears in the status bar.
Behind the scenes it's a one-time code with PKCE, and the code works only for the editor that asked for it. The editor stores its token in your OS keychain through VS Code's SecretStorage. It never sees your password.
Remote, Codespaces or browser editors: if the redirect doesn't reach the editor, the connect page shows a code. Run Pumbline: Enter Sign-in Code and paste it.
Signing out with Pumbline: Sign Out revokes that editor's access on the server. You can also see every connected editor, and disconnect any of them, under Billing → Connected editors on pumblinedev.com.
Your plan is checked when the editor starts, when its window comes back into focus, and every 15 minutes. If you upgrade in the browser, Pro unlocks as soon as you switch back. Offline, the extension uses the last plan it saw, and the server always has the final say.
Commands
| Command |
Notes |
Pumbline: Validate JSON Schema |
Selection or file |
Pumbline: Compare Prompts (Prompt Diff) |
Two Explorer files, two editors side by side, or a selection |
Pumbline: Count Tokens |
Selection, file, or several Explorer files |
Pumbline: Estimate API Cost |
Every model, cheapest first |
Pumbline: Visualize Context Window |
Adds the file or selection as a segment |
Pumbline: Format JSON / Format JSON (Sort Keys) / Minify JSON |
|
Pumbline: Encode Base64 / Encode Base64 (URL-safe) / Decode Base64 |
Each selection is converted in place |
Pumbline: Generate UUID |
One per cursor |
Pumbline: Convert Schema Format (Pro) |
|
Pumbline: Batch Validate Against Schema (Pro) |
Right-click a folder to use its JSON files |
Pumbline: Save to History (Pro) / Open from History (Pro) |
|
Pumbline: Sign In / Enter Sign-in Code / Sign Out / Refresh Plan / See Pro Plans |
|
None of these have default keybindings, so they won't clash with yours. To add one, open Keyboard Shortcuts and search for Pumbline.
Settings
| Setting |
Default |
|
pumbline.schema.defaultFormat |
auto |
openai, anthropic or gemini to always validate against one format |
pumbline.schema.validateOnSave |
false |
Re-validate a file on save once you've validated it |
pumbline.defaultModel |
gpt-6-sol |
Model used for token counts, cost and the context window |
pumbline.json.indent |
2 |
2, 4 or tab |
pumbline.uuid.kind |
v4 |
v4, v7, nanoid or short |
pumbline.apiBaseUrl |
https://pumblinedev.com |
For testing only. It's an application-level setting, so a workspace can't change where you sign in. |
Privacy
- The free tools make no network requests.
- When you're signed in, the extension asks pumblinedev.com for your plan. When you use a Pro tool, it sends that request.
- There's no telemetry and no tracking.
- The full policy is at pumblinedev.com/privacy.
Support
