toon-asijs — TOON Data Format for AsiJS

TOON (Token-Oriented Object Notation) adapter for the AsiJS formats layer. TOON is a compact, token-efficient encoding of the JSON data model designed for LLM/AI clients: indentation instead of braces, tabular forms for uniform arrays — ~30–60% fewer tokens than JSON in typical cases, while staying lossless for JSON-serializable values.

• Package: toon-asijs
• Status: released
• Source: packages/toon-asijs/
• Backend: official @toon-format/toon SDK

Registering the format makes AsiJS understand TOON natively: request bodies parse by Content-Type, responses (including errors and 404s) serialize to TOON, and Accept negotiation works automatically.

Installation

bun add toon-asijs

Quick Start

import { Asi } from "asijs";
import { registerToonFormat } from "toon-asijs";

registerToonFormat(); // enable TOON: negotiation + parsing + setFormat("toon")

const app = new Asi({ format: "toon" }); // default response format = TOON
// or: app.setFormat("toon");

app.post("/config", async (ctx) => {
  const body = await ctx.parseBody(); // Content-Type: application/toon → parsed
  return body;                        // serialized to TOON
});

app.listen(3000);

What becomes possible after registerToonFormat():

Capability	Behavior
new Asi({ format: "toon" })	Object results serialized to TOON
app.setFormat("toon")	Same, set at runtime
Accept: application/toon	TOON response even with JSON default
Accept: application/json	JSON response even with TOON default
Content-Type: application/toon	ctx.parseBody() decodes TOON
errors (400/500) & 404	Bodies serialized in TOON
route body validation	Validates TOON bodies (JSON/TOON/YAML by Content-Type)

What TOON looks like

# { items: [{ sku: "A1", qty: 2 }, { sku: "B2", qty: 1 }] }
items[2]{sku,qty}:
  A1,2
  B2,1

The tabular header declares length + fields; rows are delimiter-separated — far cheaper than [{...},{...}]. decode() returns plain JS objects, so TypeBox validation, response serializers and the whole AsiJS stack work unchanged.

API

createToonFormat(options?) → DataFormat

Creates a TOON format object (structural match for AsiJS DataFormat). Pure — only needs @toon-format/toon, so it works without AsiJS in plain fetch servers or CLI tools:

import { createToonFormat } from "toon-asijs";
import { registerFormat } from "asijs";

registerFormat(createToonFormat({ delimiter: "\t", strict: true }));

Option	Type	Default	Description
indentSize	number	2	Spaces per indentation level
delimiter	"," | "\t" | "|"	","	Separator for array values / tabular rows
strict	boolean	true	Strict decoding — array counts, indentation, duplicate keys

getToonFormat(options?) → DataFormat

Cached TOON format singleton — repeated calls return the same instance.

registerToonFormat(options?) → DataFormat

Creates the format and registers it with AsiJS, enabling everything in the table above. Idempotent. Loads AsiJS lazily, so createToonFormat stays usable without it.

MIME types

Field	Value
Canonical content type	application/toon
Aliases	text/toon, application/x-toon
Extension	.toon

Development

cd packages/toon-asijs
bun install
bun run typecheck   # tsc --noEmit
bun test            # bun test (21 unit tests)
bun run build       # bun build → dist/

The integration test (test/toon-asijs.test.ts in the repo root) exercises the full path against the real core: registration → setFormat → parseBody → negotiation → error/404 bodies → compiled routes (app.compile()).

Roadmap (TODO.md 3.2b)

• [x] TOON DataFormat adapter over @toon-format/toon (createToonFormat)
• [x] registerToonFormat() — one-call enablement (negotiation + parsing + setFormat("toon"))
• [x] Format-aware route body validation (ctx.json() → ctx.parseBody() in wrapHandler + compiled paths)
• [x] Integration tests: round-trips, options, negotiation, errors, compiled routes