Tool Input Validation and Error Handling

def search_web(query, num_results=5):
  # Validate query is a string
  if not isinstance(query, str):
    return {"error": "Parameter 'query' must be a string. You provided: " + str(type(query))}
  
  # Validate num_results is an integer
  if not isinstance(num_results, int):
    return {"error": "Parameter 'num_results' must be an integer. You provided: " + str(num_results)}
  
  # Validate num_results is in range
  if num_results < 1 or num_results > 10:
    return {"error": "Parameter 'num_results' must be between 1 and 10. You provided: " + str(num_results)}
  
  # Now proceed
  return do_search(query, num_results)

def fetch_page(url):
  # Validate URL format
  if not url.startswith("http"):
    return {"error": "Parameter 'url' must start with http:// or https://. You provided: " + url}
  
  # Validate URL length
  if len(url) > 2048:
    return {"error": "Parameter 'url' is too long (max 2048 characters)"}
  
  # Now proceed
  return do_fetch(url)

return {"error": "Invalid input"}

return {
  "error": "Parameter 'num_results' must be an integer between 1 and 10. You provided: 25. Please retry with a value like 5 or 10."
}

def search_web(query):
  try:
    result = call_search_api(query)
    return result
  except ConnectionError as e:
    return {"error": "Could not connect to search service. The service may be down. Please try again in a few seconds."}
  except TimeoutError as e:
    return {"error": "Search request timed out. Try a simpler query with fewer words."}
  except Exception as e:
    return {"error": f"Unexpected error: {str(e)}"}

"Result: Some text that looks different every time"

{
  "status": "success",
  "query": "what I searched for",
  "results": [
    {"title": "...", "snippet": "...", "url": "..."}
  ],
  "total_results": 42
}

def fetch_webpage(url, max_length=5000):
  """Fetch the full text of a webpage.
  
  Args:
    url: The URL to fetch (required)
    max_length: Maximum characters to return (optional, default: 5000)
  
  Returns:
    Dict with 'status', 'title', 'text', 'length'
    Or dict with 'error' if something goes wrong
  """
  
  # Validate url
  if not isinstance(url, str):
    return {"error": f"Parameter 'url' must be a string, not {type(url).__name__}"}
  
  if not url.startswith(("http://", "https://")):
    return {"error": f"Parameter 'url' must start with http:// or https://. You provided: {url}"}
  
  # Validate max_length
  if not isinstance(max_length, int):
    return {"error": f"Parameter 'max_length' must be an integer, not {type(max_length).__name__}"}
  
  if max_length < 100 or max_length > 50000:
    return {"error": f"Parameter 'max_length' must be between 100 and 50000. You provided: {max_length}"}
  
  # Try to fetch
  try:
    page_text = call_fetch_api(url)
    
    if page_text is None:
      return {"error": f"Could not fetch {url}. The page may not exist or may be blocked."}
    
    # Truncate if too long
    if len(page_text) > max_length:
      page_text = page_text[:max_length] + "...[truncated]"
    
    return {
      "status": "success",
      "url": url,
      "text": page_text,
      "length": len(page_text)
    }
  
  except Exception as e:
    return {"error": f"Error fetching {url}: {str(e)}"}