drf-tool-schema

Generate function-calling tool schemas from Django REST Framework serializers. Compatible with any LLM provider that follows the OpenAI tool calling standard — including OpenAI, Anthropic Claude, OpenRouter, Groq, Mistral, and LiteLLM.

Instead of writing tool schemas by hand and keeping them in sync with your serializers manually, drf-tool-schema introspects the serializer and builds the schema automatically. Change a field in your serializer and the tool schema updates with it.

Installation

pip install drf-tool-schema

Usage

from drf_tool_schema import schema_from_serializer
from partners.serializers import PartnerWriteSerializer

SCHEMAS = [
    schema_from_serializer(
        name="create_customer",
        description="Creates a new customer in the system. Returns the created customer ID.",
        serializer=PartnerWriteSerializer(),
        required_override=["legal_name", "tax_id"],
    ),
]

This produces:

{
  "type": "function",
  "function": {
    "name": "create_customer",
    "description": "Creates a new customer in the system. Returns the created customer ID.",
    "parameters": {
      "type": "object",
      "properties": {
        "legal_name": { "type": "string", "description": "Official registered company name." },
        "tax_id":     { "type": "string", "description": "NIF / CIF / VAT number." },
        "country":    { "type": "string", "description": "ISO 3166-1 alpha-2 country code.", "default": "ES" }
      },
      "required": ["legal_name", "tax_id"]
    }
  }
}

Pass the schema directly to your LLM client:

# OpenAI
client.chat.completions.create(model="gpt-4o", messages=[...], tools=SCHEMAS)

# Anthropic Claude
client.messages.create(model="claude-sonnet-4-20250514", messages=[...], tools=SCHEMAS)

# OpenRouter / Groq / Mistral / any OpenAI-compatible provider
client.chat.completions.create(model="...", messages=[...], tools=SCHEMAS)

Parameters

Parameter	Type	Description
name	str	Tool name in snake_case
description	str	Description sent to the LLM
serializer	Serializer	Instantiated DRF serializer
required_override	list[str] | None	Override required fields. If None, uses serializer's required flags
exclude	list[str] | None	Field names to exclude (read-only fields are always excluded)

Field type mapping

DRF field	JSON Schema type
CharField, EmailField, URLField, DateField, DateTimeField, UUIDField	string
IntegerField	integer (with minimum / maximum if set)
DecimalField, FloatField	number
BooleanField	boolean
ChoiceField	string + enum
ListField	array
Nested Serializer	object (inlined)

Fields with read_only=True are always excluded. Field descriptions come from help_text, falling back to label.

Development

pip install -e ".[dev]"
pytest
# or without pytest:
python tests/test_builder.py

License

MIT