Often, multiple components within the same category subdirectory (e.g., several tools under tools/payments/) might need to share utility functions, client initializations, or Pydantic models. For this, GolfMCP supports common.py files.
  • A file named common.py in any subdirectory of tools/, resources/, or prompts/ can contain shared code.
  • Other component files in the same directory or its subdirectories can import from this common.py using relative imports.
Example: tools/payments/common.py: 
# tools/payments/common.py
import httpx

# Shared HTTP client for payment operations
payment_client = httpx.AsyncClient(base_url="https://api.payments.example.com")

DEFAULT_CURRENCY = "USD"

class PaymentError(Exception):
    pass

# Mock payment processing functions for examples
async def create_charge(amount: float, token: str, description: str = "") -> dict:
    # In a real implementation, this would call the payment API
    return {"id": f"ch_{token[:8]}", "amount": amount, "currency": DEFAULT_CURRENCY}

async def create_refund(charge_id: str, amount: float = None, reason: str = "") -> dict:
    # In a real implementation, this would call the payment API
    return {"id": f"re_{charge_id[3:11]}", "charge_id": charge_id, "amount": amount}
tools/payments/charge.py: 
# tools/payments/charge.py
"""Tool to process a payment charge."""
from typing import Annotated
from pydantic import BaseModel, Field
from .common import payment_client, create_charge, PaymentError

class ChargeOutput(BaseModel):
    success: bool
    charge_id: str
    message: str

async def charge(
    amount: Annotated[float, Field(
        description="Amount to charge in USD",
        gt=0,  # Must be greater than 0
        le=10000  # Maximum charge limit
    )],
    card_token: Annotated[str, Field(
        description="Tokenized payment card identifier",
        pattern=r"^tok_[a-zA-Z0-9]+$"  # Validate token format
    )],
    description: Annotated[str, Field(
        description="Optional payment description",
        max_length=200
    )] = ""
) -> ChargeOutput:
    """Process a payment charge."""
    try:
        # Use the shared payment client from common.py
        charge_result = await create_charge(
            amount=amount,
            token=card_token,
            description=description
        )
        
        return ChargeOutput(
            success=True,
            charge_id=charge_result["id"],
            message=f"Successfully charged ${amount:.2f}"
        )
    except Exception as e:
        raise PaymentError(f"Charge failed: {e}")

export = charge
The GolfMCP build system understands these relative imports and ensures that the common.py modules are correctly packaged and accessible in the final dist/ output. The ImportTransformer in golf.core.transformer handles rewriting these imports to be absolute paths relative to the generated components directory structure.