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

首先定位 enhance 和 extract 工具的 Python MCP 入口點，並檢查它們的選用 schema 欄位如何傳遞給伺服器。使用此 issue 中的 payload 重現這些呼叫，然後確認 null、空值和省略的選用值不再觸發回報的型別錯誤，同時確保 search_web 不受影響。

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