diff --git a/pyproject.toml b/pyproject.toml
index 0c3405b..50e0f84 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -10,7 +10,7 @@ tokencost = ["model_prices.json"]
 
 [project]
 name = "tokencost"
-version = "0.1.12"
+version = "0.1.13"
 authors = [
   { name = "Trisha Pan", email = "trishaepan@gmail.com" },
   { name = "Alex Reibman", email = "areibman@gmail.com" },
diff --git a/tests/test_costs.py b/tests/test_costs.py
index d27fee1..8b3f5f6 100644
--- a/tests/test_costs.py
+++ b/tests/test_costs.py
@@ -45,6 +45,8 @@
         ("gpt-4-1106-preview", 15),
         ("gpt-4-vision-preview", 15),
         ("gpt-4o", 15),
+        ("azure/gpt-4o", 15),
+        ("claude-2.1", 4),
     ],
 )
 def test_count_message_tokens(model, expected_output):
@@ -71,6 +73,9 @@ def test_count_message_tokens(model, expected_output):
         ("gpt-4-1106-preview", 17),
         ("gpt-4-vision-preview", 17),
         ("gpt-4o", 17),
+        ("azure/gpt-4o", 17),
+        ("claude-2.1", 4),
+
     ],
 )
 def test_count_message_tokens_with_name(model, expected_output):
@@ -110,7 +115,8 @@ def test_count_message_tokens_invalid_model():
         ("gpt-4-1106-preview", 4),
         ("gpt-4-vision-preview", 4),
         ("text-embedding-ada-002", 4),
-        ("gpt-4o", 4)
+        ("gpt-4o", 4),
+        ("claude-2.1", 4)
     ],
 )
 def test_count_string_tokens(model, expected_output):
@@ -148,6 +154,9 @@ def test_count_string_invalid_model():
         (MESSAGES, "gpt-4-0613", Decimal("0.00045")),
         (MESSAGES, "gpt-4-1106-preview", Decimal("0.00015")),
         (MESSAGES, "gpt-4-vision-preview", Decimal("0.00015")),
+        (MESSAGES, "gpt-4o", Decimal("0.000075")),
+        (MESSAGES, "azure/gpt-4o", Decimal("0.000075")),
+        (MESSAGES, "claude-2.1", Decimal("0.000032")),
         (STRING, "text-embedding-ada-002", Decimal("0.0000004")),
     ],
 )
@@ -182,6 +191,9 @@ def test_invalid_prompt_format():
         (STRING, "gpt-4-0613", Decimal("0.00024")),
         (STRING, "gpt-4-1106-preview", Decimal("0.00012")),
         (STRING, "gpt-4-vision-preview", Decimal("0.00012")),
+        (STRING, "gpt-4o", Decimal("0.000060")),
+        (STRING, "azure/gpt-4o", Decimal("0.000060")),
+        (STRING, "claude-2.1", Decimal("0.000096")),
         (STRING, "text-embedding-ada-002", 0),
     ],
 )
diff --git a/tokencost/costs.py b/tokencost/costs.py
index ce29d0d..3677d6f 100644
--- a/tokencost/costs.py
+++ b/tokencost/costs.py
@@ -41,7 +41,7 @@ def count_message_tokens(messages: List[Dict[str, str]], model: str) -> int:
     """
     model = model.lower()
     model = strip_ft_model_name(model)
-    
+
     if "claude-" in model:
         """
         Note that this is only accurate for older models, e.g. `claude-2.1`. 
@@ -49,8 +49,8 @@ def count_message_tokens(messages: List[Dict[str, str]], model: str) -> int:
         instead you should rely on the `usage` property in the response for exact counts.
         """
         prompt = "".join(message["content"] for message in messages)
-        return count_string_tokens(prompt,model)
-        
+        return count_string_tokens(prompt, model)
+
     try:
         encoding = tiktoken.encoding_for_model(model)
     except KeyError:
@@ -116,12 +116,20 @@ def count_string_tokens(prompt: str, model: str) -> int:
         int: The number of tokens in the text string.
     """
     model = model.lower()
+
+    if "/" in model:
+        model = model.split("/")[-1]
+
     if "claude-" in model:
         """
         Note that this is only accurate for older models, e.g. `claude-2.1`. 
         For newer models this can only be used as a _very_ rough estimate, 
         instead you should rely on the `usage` property in the response for exact counts.
         """
+        if "claude-3" in model:
+            logger.warning(
+                "Warning: Claude-3 models are not yet supported. Returning num tokens assuming claude-2.1."
+            )
         client = anthropic.Client()
         token_count = client.count_tokens(prompt)
         return token_count