feat: better error handling.

src/mcp_cordra/client.py

@@ -32,6 +32,11 @@ class CordraNotFoundError(CordraClientError):
     pass
 
 
+class CordraAuthenticationError(CordraClientError):
+    """Exception raised for authentication/authorization failures."""
+    pass
+
+
 class CordraClient:
     """Client for interacting with Cordra repository using HTTP requests."""
 
@@ -51,6 +56,28 @@ class CordraClient:
         elif config.username or config.password:
             logger.warning("Only username or password provided, not both. Authentication may fail.")
 
+    def _handle_http_error(self, response: requests.Response, context: str) -> None:
+        """Handle HTTP errors and raise appropriate exceptions.
+        
+        Args:
+            response: The HTTP response object
+            context: Context description for the error message
+            
+        Raises:
+            CordraNotFoundError: For 404 errors
+            CordraAuthenticationError: For 401/403 errors  
+            CordraClientError: For other HTTP errors
+        """
+        status_code = response.status_code
+        if status_code == 404:
+            raise CordraNotFoundError(f"{context}: Resource not found")
+        elif status_code in (401, 403):
+            raise CordraAuthenticationError(f"{context}: Authentication failed (HTTP {status_code})")
+        elif status_code >= 500:
+            raise CordraClientError(f"{context}: Server error (HTTP {status_code})")
+        else:
+            raise CordraClientError(f"{context}: HTTP error {status_code}")
+
     async def get_object(self, object_id: str) -> DigitalObject:
         """Retrieve a digital object by its ID.
         
@@ -61,22 +88,20 @@ class CordraClient:
             The full digital object
             
         Raises:
+            ValueError: If object_id is empty
             CordraNotFoundError: If the object is not found
+            CordraAuthenticationError: If authentication fails
             CordraClientError: For other API errors
         """
-        try:
-            # Build URL: cordra_base_url/objects/prefix/postfix
         url = f"{self.config.cordra_url}/objects/{object_id}"
-            
-            # Add full=true parameter to get complete object details
         params = {"full": "true"}
         
+        try:
             response = self.session.get(url, params=params, timeout=self.config.timeout)
             
-            if response.status_code == 404:
+            if not response.ok:
-                raise CordraNotFoundError(f"Object not found: {object_id}")
+                self._handle_http_error(response, f"Failed to retrieve object {object_id}")
             
-            response.raise_for_status()
             cordra_obj = response.json()
             
             return DigitalObject(
@@ -88,12 +113,8 @@ class CordraClient:
                 payloads=cordra_obj.get('payloads'),
             )
             
-        except CordraNotFoundError:
-            raise
         except requests.RequestException as e:
             raise CordraClientError(f"Failed to retrieve object {object_id}: {e}") from e
-        except Exception as e:
-            raise CordraClientError(f"Failed to retrieve object {object_id}: {e}") from e
 
     async def find(self, query: str) -> list[dict[str, Any]]:
         """Find objects using a Cordra query.
@@ -105,15 +126,18 @@ class CordraClient:
             List of objects matching the query as dictionaries
             
         Raises:
-            CordraClientError: If there's an API error
+            ValueError: If query is empty
+            CordraAuthenticationError: If authentication fails
+            CordraClientError: For other API errors
         """
-        try:
-            # Use HTTP GET request to search endpoint
         url = f"{self.config.cordra_url}/search"
         params = {"query": query}
         
+        try:
             response = self.session.get(url, params=params, timeout=self.config.timeout)
-            response.raise_for_status()
+            
+            if not response.ok:
+                self._handle_http_error(response, f"Failed to search with query '{query}'")
             
             search_result = response.json()
             
@@ -125,5 +149,3 @@ class CordraClient:
         
         except requests.RequestException as e:
             raise CordraClientError(f"Failed to search with query '{query}': {e}") from e
-        except Exception as e:
-            raise CordraClientError(f"Failed to search with query '{query}': {e}") from e

src/mcp_cordra/server.py

@@ -5,7 +5,12 @@ import json
 
 from mcp.server.fastmcp import FastMCP
 
-from .client import CordraClient, CordraClientError, CordraNotFoundError
+from .client import (
+    CordraClient,
+    CordraClientError,
+    CordraNotFoundError,
+    CordraAuthenticationError,
+)
 from .config import CordraConfig
 
 # Initialize the MCP server
@@ -36,8 +41,12 @@ async def get_cordra_object(prefix: str, suffix: str) -> str:
         object_dict = digital_object.model_dump()
         return json.dumps(object_dict, indent=2)
 
-    except CordraNotFoundError as e:
+    except ValueError as e:
-        raise RuntimeError(f"Object not found: {object_id}") from e
+        raise RuntimeError(f"Invalid parameters: {e}") from e
+    except CordraNotFoundError:
+        raise RuntimeError(f"Object not found: {object_id}")
+    except CordraAuthenticationError as e:
+        raise RuntimeError(f"Authentication failed: {e}") from e
     except CordraClientError as e:
         raise RuntimeError(f"Failed to retrieve object {object_id}: {e}") from e
 
@@ -68,7 +77,9 @@ async def list_cordra_schemas() -> str:
         }
         return json.dumps(result, indent=2)
         
-    except Exception as e:
+    except CordraAuthenticationError as e:
+        raise RuntimeError(f"Authentication failed: {e}") from e
+    except CordraClientError as e:
         raise RuntimeError(f"Failed to list schemas: {e}") from e
 
 

tests/test_client.py

@@ -8,6 +8,7 @@ from mcp_cordra.client import (
     CordraClient,
     CordraClientError,
     CordraNotFoundError,
+    CordraAuthenticationError,
     DigitalObject,
 )
 from mcp_cordra.config import CordraConfig
@@ -141,11 +142,12 @@ class TestCordraClient:
         """Test object not found exception."""
         mock_response = mock_get.return_value
         mock_response.status_code = 404
+        mock_response.ok = False
 
         with pytest.raises(CordraNotFoundError) as exc_info:
             await client.get_object("test/nonexistent")
 
-        assert "Object not found: test/nonexistent" in str(exc_info.value)
+        assert "Resource not found" in str(exc_info.value)
 
     @patch('mcp_cordra.client.requests.Session.get')
     async def test_get_object_general_error(self, mock_get, client):