diff --git a/openagent_eval/exceptions/provider.py b/openagent_eval/exceptions/provider.py
index 0d47e3a..a6ed894 100644
--- a/openagent_eval/exceptions/provider.py
+++ b/openagent_eval/exceptions/provider.py
@@ -12,8 +12,11 @@ class ProviderError(OpenAgentEvalError):
         message: Human-readable error message.
         provider_name: Name of the provider that caused the error.
         details: Additional context about the error.
+        error_type: Human-readable error type label for standardized formatting.
     """
 
+    error_type: str = "Provider Error"
+
     def __init__(
         self,
         message: str,
@@ -34,10 +37,23 @@ def __init__(
         super().__init__(message=message, details=error_details)
         self.provider_name = provider_name
 
+    def __str__(self) -> str:
+        """Return standardized string: [provider] error_type: message (details)."""
+        provider_prefix = f"[{self.provider_name}] " if self.provider_name else ""
+        base = f"{provider_prefix}{self.error_type}: {self.message}"
+        if self.details:
+            details_items = {k: v for k, v in self.details.items() if k != "provider_name"}
+            if details_items:
+                details_str = ", ".join(f"{k}={v}" for k, v in details_items.items())
+                return f"{base} ({details_str})"
+        return base
+
 
 class ProviderNotFoundError(ProviderError):
     """Raised when a requested provider cannot be found."""
 
+    error_type: str = "Provider Not Found"
+
     def __init__(
         self,
         provider_name: str,
@@ -70,6 +86,8 @@ class ProviderConnectionError(ProviderError):
         original_error: The original exception that caused the connection failure.
     """
 
+    error_type: str = "Connection Error"
+
     def __init__(
         self,
         message: str,
@@ -100,6 +118,8 @@ class ProviderExecutionError(ProviderError):
         original_error: The original exception that caused the failure.
     """
 
+    error_type: str = "Execution Error"
+
     def __init__(
         self,
         message: str,
diff --git a/tests/unit/test_exceptions.py b/tests/unit/test_exceptions.py
index 448a096..387a625 100644
--- a/tests/unit/test_exceptions.py
+++ b/tests/unit/test_exceptions.py
@@ -134,27 +134,55 @@ class TestProviderError:
     """Tests for provider errors."""
 
     def test_basic_error(self) -> None:
-        """Test basic provider error."""
+        """Test basic provider error with standardized format."""
         error = ProviderError("Invalid provider")
-        assert str(error) == "Invalid provider"
+        assert str(error) == "Provider Error: Invalid provider"
+        assert error.error_type == "Provider Error"
+
+    def test_error_with_provider_name(self) -> None:
+        """Test provider error with provider name in standardized format."""
+        error = ProviderError(
+            "API key not found",
+            provider_name="openai",
+        )
+        assert str(error) == "[openai] Provider Error: API key not found"
 
     def test_not_found_error(self) -> None:
         """Test provider not found error."""
         error = ProviderNotFoundError("my_provider", available_providers=["openai", "gemini"])
         assert error.provider_name == "my_provider"
         assert error.available_providers == ["openai", "gemini"]
+        assert error.error_type == "Provider Not Found"
+        expected = (
+            "[my_provider] Provider Not Found: "
+            "Provider not found: my_provider. Available providers: openai, gemini "
+            "(available_providers=['openai', 'gemini'])"
+        )
+        assert str(error) == expected
 
     def test_connection_error(self) -> None:
         """Test provider connection error."""
         original = ConnectionError("Connection failed")
-        error = ProviderConnectionError("Failed to connect", original_error=original)
+        error = ProviderConnectionError(
+            "Failed to connect",
+            provider_name="gemini",
+            original_error=original,
+        )
         assert error.original_error is original
+        assert error.error_type == "Connection Error"
+        assert str(error) == "[gemini] Connection Error: Failed to connect (original_error=Connection failed)"
 
     def test_execution_error(self) -> None:
         """Test provider execution error."""
         original = RuntimeError("Execution failed")
-        error = ProviderExecutionError("Failed", original_error=original)
+        error = ProviderExecutionError(
+            "API call failed",
+            provider_name="anthropic",
+            original_error=original,
+        )
         assert error.original_error is original
+        assert error.error_type == "Execution Error"
+        assert str(error) == "[anthropic] Execution Error: API call failed (original_error=Execution failed)"
 
 
 class TestPluginError: