The `enhance` and `extract` tools always throw a server-side error when called, making them unusable via MCP.

Bug

The enhance and extract tools always throw a server-side error when called, making them unusable via MCP.

Error

Error calling tool 'enhance': Invalid variable type: value should be str, int or float, got None of type <class 'NoneType'>
Error calling tool 'extract': Invalid variable type: value should be str, int or float, got None of type <class 'NoneType'>

Root cause

The tool schemas declare several parameters as anyOf: [string, null] (e.g. location, employer, title, school, page_type), meaning null is a valid value per the schema. However the Python server rejects None at runtime with the
above error.

This happens whether the optional fields are passed explicitly as null, passed as empty strings, or omitted entirely — the MCP framework appears to populate unset optional fields as None, which the server then rejects.

Reproduction

Call enhance with any valid Person lookup:

{                                                                                                                                                                                                                                                 
  "type": "Person",       
  "name": ["Connor Leech"],
  "email": ["connor@example.com"],
  "employer": "Acme",                                                                                                                                                                                                                             
  "title": "Engineer",
  "url": [],                                                                                                                                                                                                                                      
  "location": null,                                                                                                                                                                                                                               
  "school": null
}                                                                                                                                                                                                                                                 
                          
Call extract with just a URL:
{
  "url": "https://example.com",
  "format": "markdown"         
}                                                                                                                                                                                                                                                 
 
Both fail. search_web works correctly.                                                                                                                                                                                                            
                                                                                                                                                                                                                                                  
Expected behavior
                                                                                                                                                                                                                                                  
Optional parameters that are null or omitted should be handled gracefully by the server (ignored or treated as unset).                                                                                                                            
 
Environment                                                                                                                                                                                                                                       
                          
- Remote MCP server: https://mcp.diffbot.com/mcp?token=...                                                                                                                                                                                        
- MCP client: Claude Code CLI

Beginne damit, die Python-MCP-Einstiegspunkte für die Tools enhance und extract zu lokalisieren und zu prüfen, wie ihre optionalen Schemafelder an den Server übergeben werden. Reproduziere die Aufrufe mit den Payloads aus diesem Issue und verifiziere anschließend, dass null, leere und ausgelassene optionale Werte nicht mehr den gemeldeten Typfehler auslösen, während search_web weiterhin unbeeinträchtigt bleibt.