slimschema 0.0.1.dev7

Token-efficient schema language for LLMs with fast Zig backend

SlimSchema

SlimSchema is a schema toolkit with two entry points:

• SlimSchema YAML (Zig-first): a compact, YAML-shaped schema language for token-efficient prompts and interop.
• Spec API (typed-first): derive JSON Schema + validation from language types:
  • Python: @spec decorator on dataclasses
  • Zig: Spec(T) for comptime schema generation

Both surfaces are intended to share the same core concepts (constraints, formats, defaults, error paths) while targeting different workflows.

Python Quickstart (@spec)

uv pip install slimschema
pip install slimschema

from typing import Annotated

from slimschema import Alias, Len, Range, spec


@spec
class User:
    user_name: Annotated[str, Alias("userName"), Len(1, 50)]
    age: Annotated[int, Range(0, 120)]

# Load from JSON (mirrors json.loads)
user = User.loads('{"userName": "Alice", "age": 30}')
assert user.user_name == "Alice"
assert user.age == 30

# Dump to JSON (mirrors json.dumps)
json_str = user.dumps()

# Load from dict (mirrors json.load)
user2 = User.load({"userName": "Bob", "age": 25})

# Dump to dict (mirrors dataclasses.asdict)
data = user2.dump()
assert data == {"userName": "Bob", "age": 25}

Zig Quickstart (YAML + Spec(T))

YAML DSL:

const slimschema = @import("slimschema");

const yaml =
    \\name: str{1..50}
    \\age: 0..120
;

Typed spec:

const slimschema = @import("slimschema");

const User = struct { name: []const u8, age: i64 };
pub const user_json_schema = slimschema.jsonSchemaFromType(User);

SlimSchema YAML (Full Spec)

# Primitives
name: str                    # string
age: int                     # integer
score: float                 # floating point number
active: bool                 # boolean (true/false)
meta: obj                    # any object/dict
anything: any                # any JSON value

# Format types (validated)
email: email                 # email address
website: url                 # URL (http/https)
birthday: date               # date (YYYY-MM-DD)
timestamp: datetime          # ISO datetime
user_id: uuid                # UUID format

# Constraints
username: str{3..50}         # string length 3-50 chars
age_range: 18..120           # integer range 18-120
code: /^[A-Z]{3}$/           # regex pattern match

# Collections
tags: list[str]              # array of strings
unique_ids: set[int]         # array of unique integers
coords: tuple[float, float]  # fixed-length tuple [x, y]
scores: dict[str, int]       # object with string keys, int values

# Enums and Unions
status: active | pending     # enum: one of these values
value: str | int             # union: string OR integer

# Optional vs Nullable
?nickname: str               # ? prefix: field can be omitted
rating: float?               # ? suffix: value can be null
?notes: str?                 # both: omittable AND nullable

# Hidden fields (excluded from LLM prompts)
_internal_id: str            # _ prefix: hidden field
_?debug_info: str            # hidden + optional

# Default values
count: int = 0               # literal default
role: str = "user"           # quoted string default
items: list = []             # empty list default
config: dict = {}            # empty dict default

# Default generators (auto-generated if omitted)
id: uuid = uuid              # UUID v4
id_v7: uuid = uuid7          # UUID v7 (time-ordered)
id_ulid: str = ulid          # ULID (sortable, 26 chars)
id_xid: str = xid            # XID (compact, 20 chars)
id_nano: str = nanoid        # NanoID (URL-safe, 21 chars)
created: datetime = now      # current UTC datetime
day: date = today            # current UTC date
ts: int = epoch              # unix timestamp (seconds)

# Nested objects (indentation-based)
user:                        # parent field with nested structure
  name: str                  # child field
  age: int
  address:                   # deeply nested
    street: str
    city: str
    zip: str{5..10}

# Inline objects (single-line syntax)
point: {x: float, y: float}  # compact object definition

# YAML list syntax (array of objects)
issues:                      # parent field becomes array
  - file: str                # first field on dash line
    line: int                # additional fields indented
    severity: str
    message: str

# Complex example: API response schema
response:
  success: bool
  data:
    total: int
    page: 1..100
    items:                   # nested list
      - id: uuid
        name: str{1..100}
        ?tags: list[str]
        created: datetime
  ?error: str

Documentation

• docs/README.md (start here)
• docs/WHY.md (architecture decisions: Python/Zig split, when to use each API)
• docs/python/README.md (Python @spec)
• docs/zig/README.md (Zig YAML + Spec(T))
• docs/dev-guide.md (development workflow)
• DOCS_INVENTORY.md (doc gaps + migration plan)

Development

make build
make test
make coverage

Zig tests:

cd zig && zig build test

License

MIT