JSON Schema DSL

A simple DSL to generate JSON Schema with one-liner style.

Why JSON Schema DSL?

1. Make JSON Schema concise:

2. AI friendly: Function calling, Structured Output with simple DSL:

3. Schema friendly for CSV, Excel, Text2SQL:

Get Started

CLI: cargo install json-schema-dsl

$ json-schema-dsl "User{ id: int, name: string, email: Email}"

Output as following:

{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "title": "User",
  "type": "object",
  "properties": {
    "id": {
      "type": "integer"
    },
    "name": {
      "type": "string"
    },
    "email": {
      "type": "string",
      "format": "email"
    }
  },
  "required": [
    "id",
    "name",
    "email"
  ]
}

Rust library: cargo add json-schema-dsl serde_json

fn main() {
    let struct_text = "User {id: int, name: string, email: Email}";
    let json_schema = json_schema_dsl::to_json_schema(struct_text).unwrap();
    println!("{}", serde_json::to_string_pretty(&json_schema).unwrap());
}

Syntax

User { id: int, name: string, birth_date: Date, email?: Email, tags: List<string>}

• Object Name: starts with capital character, such as ObjectName { field: type }.
• Field name: starts with lower-case character.
• Optional field: field?: type

Basic Types

JSON Schema basic types:

• string: aliases: varchar, Text, String, bytes or bytea(base64)
• integer: aliases: int, bigint, long, serial, bigserial,int32, int64, int96, int128
• number: aliases: float, double, real, decimal
• boolean: aliases: bool

Extra Types

Extra types are for semantic meaning, and they are all string type.

• Path: /path/to/file
• S3Path: s3://bucket/key
• Ulid or ULID
• Color: #F7F8FA
• Isbn or ISBN: 978-3-16-148410-0
• SemVer: 1.2.3
• PhoneNumber: +1-202-555-0192
• CreditCard: 4111 1111 1111 1111
• Currency: USD, CNY
• Language: en, zh-CN
• Locale: en-US, zh-CN
• MimeType: application/json
• Base64: base64 encoded string

array Types

array type is alike List<T>, and T is a basic type or format name.

• List: aliases: list
• Array: aliases: array
• Set(uniqueItems): aliases: set

object Type

Declare object type: field: ObjectName {field: type}.

Attention: ObjectName should start with Capital Character.

Formats

JSON Schema formats, and name should start with a capital letter:

• Date
• Time
• Datetime
• Timestamp
• Interval
• Duration
• Email
• Hostname
• Domainname
• Ipv4
• Ipv6
• Uri
• Uuid or UUID
• Json or JSON: JSON text
• Xml or XML: XML text

Misc

• range: age: int(18,), age: int(,150) or age: int(1,18)
• string length range: nick: string(6,32), varchar(32)
• array items length range: list<string>(2), list<float>(1536)
• tuple: income: [int, string]
• enum: enum('a', 'b', 'c') or enum(1, 2, 3)
• regex: regex('^[a-z]+$')
• anyOf: field: type1|type2, no space between types
• additionalProperties: {field: type, ...}, ellipsis before }.

References

• JSON Schema: https://json-schema.org/
• JSON Schema formats: https://json-schema.org/understanding-json-schema/reference/string#built-in-formats
• M-Schema: a semi-structure representation of database schema - https://github.com/XGenerationLab/M-Schema