Crate rustapi_toon 

TOON Format Support for RustAPI

This crate provides TOON (Token-Oriented Object Notation) support for the RustAPI framework. TOON is a compact, human-readable format designed for passing structured data to Large Language Models (LLMs) with significantly reduced token usage (typically 20-40% savings).

Quick Example

JSON (16 tokens, 40 bytes):

{
  "users": [
    { "id": 1, "name": "Alice" },
    { "id": 2, "name": "Bob" }
  ]
}

TOON (13 tokens, 28 bytes) - 18.75% token savings:

users[2]{id,name}:
  1,Alice
  2,Bob

Usage

Add to your Cargo.toml:

[dependencies]
rustapi-rs = { version = "0.1", features = ["toon"] }

Toon Extractor

Parse TOON request bodies:

use rustapi_rs::prelude::*;
use rustapi_rs::toon::Toon;

#[derive(Deserialize)]
struct CreateUser {
    name: String,
    email: String,
}

async fn create_user(Toon(user): Toon<CreateUser>) -> impl IntoResponse {
    Json(user)
}

Toon Response

Return TOON formatted responses:

use rustapi_rs::prelude::*;
use rustapi_rs::toon::Toon;

#[derive(Serialize)]
struct User {
    id: u64,
    name: String,
}

async fn get_user() -> Toon<User> {
    Toon(User {
        id: 1,
        name: "Alice".to_string(),
    })
}

Content Types

• Request: application/toon or text/toon
• Response: application/toon

Modules

decode

Decoder Implementation

encode

Encoder Implementation

Structs

AcceptHeader

Parsed Accept header with quality values

DecodeOptions

Options for decoding TOON format to JSON values.

EncodeOptions

Options for encoding JSON values to TOON format.

LlmResponse

LLM-optimized response wrapper with token counting.

MediaTypeEntry

A single media type entry from Accept header

Negotiate

Content-negotiated response wrapper

Toon

TOON body extractor and response type

Enums

OutputFormat

Supported output formats

ToonError

Error type for TOON operations

Constants

JSON_CONTENT_TYPE

JSON Content-Type

TOON_CONTENT_TYPE

TOON Content-Type header value

TOON_CONTENT_TYPE_TEXT

Alternative TOON Content-Type (text-based)

TOON_FORMAT_DESCRIPTION

TOON format description for OpenAPI

X_FORMAT_USED

Header name for format used

X_TOKEN_COUNT_JSON

Header name for JSON token count

X_TOKEN_COUNT_TOON

Header name for TOON token count

X_TOKEN_SAVINGS

Header name for token savings percentage

Functions

api_description_with_toon

OpenAPI info description with TOON support notice

decode

Decode a TOON string into any deserializable type.

decode_default

Decode with default options (strict mode, type coercion enabled).

encode

Encode any serializable value to TOON format.

encode_default

Encode with default options (2-space indent, comma delimiter).

format_comparison_example

Generate example responses showing JSON vs TOON

token_headers_schema

Schema for token comparison headers

toon_extension

Generate OpenAPI vendor extension for TOON support

toon_schema

Generate OpenAPI schema for TOON format