diff --git a/README.md b/README.md
index 1a5b81d..1340059 100644
--- a/README.md
+++ b/README.md
@@ -11,9 +11,9 @@ pip install paysgator
 ## Usage
 
 ```python
-from paysgator import PaysgatorClient
-
-client = PaysgatorClient(api_key="YOUR_API_KEY")
+import os; from paysgator import PaysgatorClient
+# WARNING: Never hardcode API keys. Use environment variables.
+client = PaysgatorClient(api_key=os.getenv("PAYSGATOR_API_KEY"))
 
 # Create a payment
 payment = client.payments.create(
diff --git a/pyproject.toml b/pyproject.toml
index ff08145..68cc74a 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -10,7 +10,7 @@ authors = [
 ]
 description = "Official Python SDK for Paysgator API"
 readme = "README.md"
-requires-python = ">=3.7"
+requires-python = ">=3.8"
 classifiers = [
     "Programming Language :: Python :: 3",
     "License :: OSI Approved :: MIT License",
diff --git a/src/paysgator/__init__.py b/src/paysgator/__init__.py
index d0cf227..b9ae5d7 100644
--- a/src/paysgator/__init__.py
+++ b/src/paysgator/__init__.py
@@ -1,4 +1,4 @@
-from .client import PaysgatorClient
+from .client import PaysgatorClient, Payments, Subscriptions
 from .exceptions import PaysgatorError, AuthenticationError, APIError
 
-__all__ = ["PaysgatorClient", "PaysgatorError", "AuthenticationError", "APIError"]
+__all__ = ["PaysgatorClient", "Payments", "Subscriptions", "PaysgatorError", "AuthenticationError", "APIError"]
diff --git a/src/paysgator/client.py b/src/paysgator/client.py
index a067367..18ce640 100644
--- a/src/paysgator/client.py
+++ b/src/paysgator/client.py
@@ -50,10 +50,11 @@ def get_balance(self) -> WalletBalanceResponse:
         return WalletBalanceResponse(**response_data)
 
 class PaysgatorClient:
-    BASE_URL = "https://paysgator.com/api/v1"
 
     def __init__(self, api_key: str):
         self.api_key = api_key
+        self.base_url = "https://paysgator.com/api/v1"
+
         self.session = requests.Session()
         self.session.headers.update({
             "X-Api-Key": self.api_key,
@@ -66,11 +67,11 @@ def __init__(self, api_key: str):
         self.wallet = Wallet(self)
 
     def set_base_url(self, url: str):
-        self.BASE_URL = url
+        self.base_url = url
 
     def request(self, method: str, endpoint: str, data: Optional[dict] = None) -> dict:
-        url = f"{self.BASE_URL}{endpoint}"
-        response = self.session.request(method, url, json=data)
+        url = f"{self.base_url}{endpoint}"
+        response = self.session.request(method, url, json=data, timeout=30)
         
         if response.status_code >= 400:
              raise APIError(response.status_code, response.text)
diff --git a/src/paysgator/exceptions.py b/src/paysgator/exceptions.py
index 3067741..d7d7f27 100644
--- a/src/paysgator/exceptions.py
+++ b/src/paysgator/exceptions.py
@@ -1,6 +1,10 @@
 class PaysgatorError(Exception):
     """Base exception for Paysgator SDK"""
-    pass
+    def __init__(self, message: str = "", endpoint=None, method=None, response_body=None):
+        self.endpoint = endpoint
+        self.method = method
+        self.response_body = response_body
+        super().__init__(message)
 
 class AuthenticationError(PaysgatorError):
     """Raised when authentication fails"""
@@ -8,7 +12,7 @@ class AuthenticationError(PaysgatorError):
 
 class APIError(PaysgatorError):
     """Raised when the API returns an error"""
-    def __init__(self, status_code: int, message: str):
+    def __init__(self, status_code: int, message: str, endpoint=None, method=None, response_body=None):
         self.status_code = status_code
         self.message = message
-        super().__init__(f"API Error {status_code}: {message}")
+        super().__init__(f"API Error {status_code}: {message}", endpoint, method, response_body)
diff --git a/src/paysgator/models.py b/src/paysgator/models.py
index 8863e2d..de53545 100644
--- a/src/paysgator/models.py
+++ b/src/paysgator/models.py
@@ -7,8 +7,8 @@ class Mode(str, Enum):
     TEST = "TEST"
 
 class PaymentCreateRequest(BaseModel):
-    amount: float
-    currency: str
+    amount: float = Field(..., gt=0)
+    currency: str = Field(..., min_length=3, max_length=3)
     external_transaction_id: Optional[str] = Field(None, alias="externalTransactionId")
     payment_methods: Optional[List[str]] = Field(None, alias="payment_methods")
     fields: Optional[List[str]] = None
@@ -62,8 +62,8 @@ class SubscriptionResponse(BaseModel):
 
 class TransactionResponse(BaseModel):
     id: str
-    amount: float
-    currency: str
+    amount: float = Field(..., gt=0)
+    currency: str = Field(..., min_length=3, max_length=3)
     status: str
     method: Optional[str] = None
     description: Optional[str] = None
@@ -72,6 +72,6 @@ class TransactionResponse(BaseModel):
 
 class WalletBalanceResponse(BaseModel):
     wallet_id: str = Field(..., alias="walletId")
-    currency: str
+    currency: str = Field(..., min_length=3, max_length=3)
     balance: str
     mode: str
diff --git a/test_sdk.py b/test_sdk.py
index 7ee8b76..4078c13 100644
--- a/test_sdk.py
+++ b/test_sdk.py
@@ -1,10 +1,10 @@
-from src.paysgator.client import PaysgatorClient
-
+from paysgator.client import PaysgatorClient
+import os
 #Mpesa direct charge test 
 
-api_key = "<Api Key>"
+api_key = os.getenv("PAYSGATOR_API_KEY", "<Api Key>")
 
-wallet_id = "<Wallet Id>"
+wallet_id = os.getenv("PAYSGATOR_WALLET_ID", "<Wallet Id>")
 
 client = PaysgatorClient(api_key, wallet_id)