Make the tiny tool you wish existed

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Upshot renders small interactive tools from URLs generated by language models. A card can contain text, numeric inputs, choices, checkboxes, formulas, and decisions.

Ask a model that can read web pages:

read https://upshot.fyi and export this

The model reads llms.txt and returns an Upshot URL. Upshot does not call the model.

Live examples

• Split a dinner bill
• Compare savings with a runway target
• Calculate UK take-home pay with student-loan choices
• More examples

Runtime model

The card is encoded after the URL's #:

https://upshot.fyi/v2/#a=...&h=...&g=Split&i=bill:80:Bill&i=n:3:People&r=each:bill/n:Each+pays

The browser does not send the fragment to the server. The static renderer in v2/index.html parses the fragment, calculates results, and updates the URL when the reader changes a control.

The project has no application server, database, account system, build step, or runtime dependency. Anyone holding a card URL can read it. Shared URLs may be retained by browsers, chat clients, and other services used to transmit them.

Format

g= starts a block. Blocks contain these primitives:

Key	Content
p	Bullet
o	Ordered step
f	Fixed label/value row
c	Checkbox
i	Editable number
s	Exclusive numeric choice
r	Computed numeric result
t	Conditional wording
u	Display unit

The complete model-facing grammar and encoding rules are in llms.txt.

Local use

python3 -m http.server 8787

Open http://localhost:8787/.

Tests

Run the complete automated suite:

node test/run.js

Chrome is required. The suite checks prompt synchronization, transport, arithmetic, parsing, rendering, invalid fields, interactions, saved state, and Copy/Share handlers in one browser harness.

Score a local file containing one generated URL per line with:

node test/transport.js links.txt

Check that the suite would notice if the renderer were wrong:

node test/mutate.js

This breaks v2/index.html 34 ways, one at a time, and runs the suite against each. A surviving mutation is a blind spot in the tests, not a bug in the renderer. It takes about half a minute, so it is a release-time check rather than one to run on every edit.

Documentation

• HOW_IT_WORKS.md: runtime architecture and file ownership.
• LANGUAGE.md: language rules, tests, maintenance process, current bugs, and known limits.

Repository files

File	Purpose
index.html	Landing page and static authoring contract
llms.txt	Model-facing authoring contract
v2/index.html	Current parser, evaluator, and renderer
v1/index.html	Frozen previous renderer
broken/index.html	Page for a fragment with no renderable card
made/index.html	Curated static examples
scripts/sync-prompt.js	Synchronizes llms.txt with the landing page
test/	Single test suite and helper modules
test/mutate.js	Scores the suite by planting deliberate bugs

Licence

Repository code is available under the MIT Licence.

Card text is supplied in each URL and is not stored or endorsed by this repository.