sequenceDiagram
    participant Client
    participant Serializer
    participant ValidationLogic
    participant BlockConfig
    participant ToolRegistry
    
    Client->>Serializer: serializeWorkflow(blocks, validateRequired=true)
    Serializer->>Serializer: serializeBlock(block)
    Serializer->>Serializer: extractParams(block)
    
    alt validateRequired is true
        Serializer->>ValidationLogic: validateRequiredFieldsBeforeExecution(block, blockConfig, params)
        
        ValidationLogic->>BlockConfig: Check if block enabled
        
        alt Block has tools.access
            ValidationLogic->>ToolRegistry: getTool(currentToolId)
            ToolRegistry-->>ValidationLogic: currentTool
            
            loop For each tool param
                ValidationLogic->>ValidationLogic: Check if required & user-only
                ValidationLogic->>ValidationLogic: Check visibility via shouldSerializeSubBlock
                ValidationLogic->>ValidationLogic: Validate field value
            end
        end
        
        Note over ValidationLogic: NEW: Secondary validation for blocks without tools
        
        ValidationLogic->>ValidationLogic: Build validatedByTool Set
        
        loop For each subBlock in blockConfig
            alt Not validated by tool params
                ValidationLogic->>ValidationLogic: Check visibility via shouldSerializeSubBlock
                ValidationLogic->>ValidationLogic: Check if required
                ValidationLogic->>ValidationLogic: Validate field value
            end
        end
        
        alt Missing fields found
            ValidationLogic-->>Serializer: throw Error(missing fields)
            Serializer-->>Client: Error
        else All fields valid
            ValidationLogic-->>Serializer: validation passed
        end
    end
    
    Serializer->>Serializer: Continue serialization
    Serializer-->>Client: SerializedBlock