# YJTOON

> YJTOON is a free, open catalog of categorized reference datasets for AI agents and humans.
> 185 datasets across 27 categories, published as CC0 public domain data. Every dataset is
> available as JSON, YAML, and TOON (a compact encoding aimed at LLM prompts) from one URL,
> with no authentication, no API keys, and no signup. Rate limit: 120 requests per minute per IP.

Measured context: TOON produces about 40% fewer bytes than pretty-printed JSON for this data
(578,431 bytes of JSON vs 401,742 bytes of TOON across all 185 dataset files). Humans can read
any dataset as a rendered HTML table at https://yjtoon.com/catalog/.

## Human-readable catalog (HTML)

- [Catalog index](https://yjtoon.com/catalog/): all 185 datasets, grouped by category
- [Per-category pages](https://yjtoon.com/catalog/{category}): e.g. https://yjtoon.com/catalog/programming-languages/
- [Per-dataset pages](https://yjtoon.com/catalog/{category}/{dataset}): the data rendered as tables, with format links, suggested citation, and API example
- [Homepage](https://yjtoon.com/): browse by category, live format comparison, interactive voxel view of the catalog
- [TOON Studio](https://yjtoon.com/#studio): paste JSON and it is encoded in the browser by the same encoder the API uses; byte counts are exact, token counts are labelled estimates

## API endpoints (dynamic)

- [List categories](https://yjtoon.com/api/): all 27 categories with dataset counts
- [Category datasets](https://yjtoon.com/api/category/{slug}): datasets in a category (e.g. /api/category/programming-languages)
- [Single dataset](https://yjtoon.com/api/dataset/{slug}): full dataset content (e.g. /api/dataset/http-status-codes-complete)
- [Search](https://yjtoon.com/api/search?q={query}): search titles, descriptions, tags, and data (min 2 characters)
- All endpoints support ?format=json (default), ?format=yaml, ?format=toon
- Rate limit: 120 requests per minute per IP; 429 with Retry-After on exceed
- [API documentation](https://yjtoon.com/api.html): endpoints, formats, rate limits, copyable examples

## Static files (cache-friendly, no database)

- [Whole catalog in one request](https://yjtoon.com/static-data/catalog-index.json): every category and dataset summary (57 KB). TOON equivalent: https://yjtoon.com/static-data/catalog-index.toon (35 KB)
- [Category index](https://yjtoon.com/static-data/categories.json): the full catalog map
- [Per-category files](https://yjtoon.com/static-data/category/{slug}.json)
- [Per-dataset files](https://yjtoon.com/static-data/dataset/{slug}.json|.yaml|.toon)
- [Search index](https://yjtoon.com/static-data/search-index.json)

## Formats

- JSON: standard, a parser in every language; 57,257 bytes for the combined catalog index
- YAML: easier for a human to edit and read; 38,678 bytes for the same index
- TOON: compact notation for LLM prompts; 34,554 bytes for the same index. Uniform arrays of objects become tabular `[n]{key1,key2}:` blocks, and scalars are quoted only when they contain whitespace or `, : { } [ ]`
- The browser encoder (js/toon.js) and the server encoder (api/format.php) are held to byte-identical output by a test that compares all 185 datasets on every run
- [TOON grammar reference](https://yjtoon.com/blog/toon-format-grammar-spec-overview/), [a 50-line Python parser](https://yjtoon.com/blog/tiny-toon-parser-in-50-lines-of-python/)

## Blog

- [Blog index](https://yjtoon.com/blog/): 64 posts — reference guides, cheat sheets, and explainers on HTTP, SQL, Unix, data formats, and LLM tooling
- Topic clusters: TOON and encodings, agent context economics, grounding and verification, dataset publishing and SEO, HTTP behaviour for data APIs
- Popular guides: [HTTP status codes cheat sheet](https://yjtoon.com/blog/http-status-codes-cheat-sheet/), [HTTP methods](https://yjtoon.com/blog/http-methods-get-post-put-patch-delete/), [SQL join types](https://yjtoon.com/blog/sql-join-types-inner-left-right-full/), [Git commands](https://yjtoon.com/blog/git-commands-cheat-sheet/), [Unix file commands](https://yjtoon.com/blog/unix-file-commands-cheat-sheet/), [LLM glossary](https://yjtoon.com/blog/llm-glossary-key-terms/), [Cognitive biases checklist](https://yjtoon.com/blog/cognitive-biases-decision-checklist/), [Network ports](https://yjtoon.com/blog/common-network-ports-reference/)
- [RSS feed](https://yjtoon.com/blog/rss.xml)

## Book

- [Open Data for AGI](https://theknowledgeproject.gumroad.com/l/zdrla) ($4.99, PDF): the argument behind this catalog — why public, free, and open datasets decide what AI systems become. All site data remains free; the book is the synthesis, not a paywall.
- [Full ebook catalog](https://theknowledgeproject.gumroad.com/) (20 titles)

## License

CC0 — public domain. Use for any purpose, commercial included, without attribution.
Attribution is welcome but never required. Suggested citation is printed on every dataset page.