diff --git a/src/promptforge/providers/openai.py b/src/promptforge/providers/openai.py
index 837a110..1686f86 100644
--- a/src/promptforge/providers/openai.py
+++ b/src/promptforge/providers/openai.py
@@ -1,6 +1,7 @@
-import asyncio
+"""OpenAI provider implementation."""
+
 import time
-from typing import Any, AsyncIterator, Dict, Optional
+from typing import AsyncIterator, Optional
 
 from openai import AsyncOpenAI, APIError, RateLimitError, APIConnectionError
 
@@ -9,6 +10,8 @@ from ..core.exceptions import ProviderError
 
 
 class OpenAIProvider(ProviderBase):
+    """OpenAI GPT models provider."""
+
     def __init__(
         self,
         api_key: Optional[str] = None,
@@ -17,6 +20,7 @@ class OpenAIProvider(ProviderBase):
         base_url: Optional[str] = None,
         **kwargs,
     ):
+        """Initialize OpenAI provider."""
         super().__init__(api_key, model, temperature, **kwargs)
         self.base_url = base_url
         self._client: Optional[AsyncOpenAI] = None
@@ -26,6 +30,7 @@ class OpenAIProvider(ProviderBase):
         return "openai"
 
     def _get_client(self) -> AsyncOpenAI:
+        """Get or create OpenAI client."""
         if self._client is None:
             api_key = self.api_key or self._get_api_key_from_env()
             if not api_key:
@@ -33,7 +38,10 @@ class OpenAIProvider(ProviderBase):
                     "OpenAI API key not configured. "
                     "Set OPENAI_API_KEY env var or pass api_key parameter."
                 )
-            self._client = AsyncOpenAI(api_key=api_key, base_url=self.base_url)
+            self._client = AsyncOpenAI(
+                api_key=api_key,
+                base_url=self.base_url,
+            )
         return self._client
 
     def _get_api_key_from_env(self) -> Optional[str]:
@@ -47,6 +55,7 @@ class OpenAIProvider(ProviderBase):
         max_tokens: Optional[int] = None,
         **kwargs,
     ) -> ProviderResponse:
+        """Send completion request to OpenAI."""
         start_time = time.time()
 
         try:
@@ -57,9 +66,9 @@ class OpenAIProvider(ProviderBase):
                 messages.append({"role": "system", "content": system_prompt})
             messages.append({"role": "user", "content": prompt})
 
-            response = await client.chat.completions.create(
+            response = await client.chat.completions.create(  # type: ignore[arg-type]
                 model=self.model,
-                messages=messages,
+                messages=messages,  # type: ignore[arg-type]
                 temperature=self.temperature,
                 max_tokens=max_tokens,
                 **kwargs,
@@ -72,12 +81,14 @@ class OpenAIProvider(ProviderBase):
                 model=self.model,
                 provider=self.name,
                 usage={
-                    "prompt_tokens": response.usage.prompt_tokens,
-                    "completion_tokens": response.usage.completion_tokens,
-                    "total_tokens": response.usage.total_tokens,
+                    "prompt_tokens": response.usage.prompt_tokens,  # type: ignore[union-attr]
+                    "completion_tokens": response.usage.completion_tokens,  # type: ignore[union-attr]
+                    "total_tokens": response.usage.total_tokens,  # type: ignore[union-attr]
                 },
                 latency_ms=latency_ms,
-                metadata={"finish_reason": response.choices[0].finish_reason},
+                metadata={
+                    "finish_reason": response.choices[0].finish_reason,
+                },
             )
         except APIError as e:
             raise ProviderError(f"OpenAI API error: {e}")
@@ -86,13 +97,14 @@ class OpenAIProvider(ProviderBase):
         except APIConnectionError as e:
             raise ProviderError(f"OpenAI connection error: {e}")
 
-    async def stream_complete(
+    async def stream_complete(  # type: ignore[override]
         self,
         prompt: str,
         system_prompt: Optional[str] = None,
         max_tokens: Optional[int] = None,
         **kwargs,
     ) -> AsyncIterator[str]:
+        """Stream completion from OpenAI."""
         try:
             client = self._get_client()
 
@@ -101,28 +113,39 @@ class OpenAIProvider(ProviderBase):
                 messages.append({"role": "system", "content": system_prompt})
             messages.append({"role": "user", "content": prompt})
 
-            stream = await client.chat.completions.create(
+            stream = await client.chat.completions.create(  # type: ignore[arg-type]
                 model=self.model,
-                messages=messages,
+                messages=messages,  # type: ignore[arg-type]
                 temperature=self.temperature,
                 max_tokens=max_tokens,
                 stream=True,
                 **kwargs,
             )
 
-            async for chunk in stream:
+            async for chunk in stream:  # type: ignore[union-attr]
                 if chunk.choices[0].delta.content:
                     yield chunk.choices[0].delta.content
         except APIError as e:
             raise ProviderError(f"OpenAI API error: {e}")
 
     def validate_api_key(self) -> bool:
+        """Validate OpenAI API key."""
         try:
             import os
             api_key = self.api_key or os.environ.get("OPENAI_API_KEY")
             if not api_key:
                 return False
-            client = AsyncOpenAI(api_key=api_key)
+            _ = AsyncOpenAI(api_key=api_key)
             return True
         except Exception:
-            return False
\ No newline at end of file
+            return False
+
+    def list_models(self) -> list[str]:
+        """List available OpenAI models."""
+        return [
+            "gpt-4",
+            "gpt-4-turbo",
+            "gpt-4o",
+            "gpt-3.5-turbo",
+            "gpt-3.5-turbo-16k",
+        ]