matrix-fn-schema

Convert Python function signatures (type annotations + docstrings) into OpenAI-compatible JSON Schema (tool call format).

from dataclasses import dataclass
from enum import Enum
from typing import Annotated, List, Optional, Literal
from uuid import UUID
from matrix_fn_schema import build_json_schema


class Priority(int, Enum):
    LOW = 1
    MEDIUM = 2
    HIGH = 3


@dataclass
class Attachment:
    filename: str
    url: str


def create_task(
    title: Annotated[str, "Max 200 chars"],
    priority: Priority,
    assignee_id: UUID,
    attachments: List[Attachment],
    deadline: Optional[str] = None,
) -> dict:
    """Create a new task."""
    ...


schema = build_json_schema(create_task)

Result:

{
  "type": "function",
  "name": "create_task",
  "description": "Create a new task.",
  "strict": true,
  "parameters": {
    "type": "object",
    "properties": {
      "title":         {"type": "string"},
      "priority":      {"type": "integer", "enum": [1, 2, 3]},
      "assignee_id":   {"type": "string", "format": "uuid"},
      "attachments":   {"type": "array", "items": {"type": "object", "properties": {
                          "filename": {"type": "string"},
                          "url": {"type": "string"}
                        }, "required": ["filename", "url"], "additionalProperties": false}},
      "deadline":      {"anyOf": [{"type": "string"}, {"type": "null"}]}
    },
    "additionalProperties": false,
    "required": ["title", "priority", "assignee_id", "attachments", "deadline"]
  }
}

Supported types

Requirements

Python 3.10+. Dependencies: docstring-parser>=0.16.

Optional: pydantic>=2 for BaseModel support.

Written with love by dotmatrix.