ComfyUI MCP Server

Instructions

Implementation Reference

• comfy_mcp/mcp/server.py:419-491 (handler)

  MCP tool handler for 'generate_from_template'. Orchestrates template retrieval, parameter validation, DSL generation via TemplateManager, optional file saving, and result formatting.

  @mcp.tool
  def generate_from_template(
      template_name: str,
      parameters: dict = None,
      save_path: str = None
  ) -> dict:
      """Generate a workflow from a template with custom parameters.
      
      Creates a complete DSL workflow by substituting parameters into
      the template. Optionally saves to file.
      
      Args:
          template_name: Name of the template to use
          parameters: Dictionary of parameter values to substitute
          save_path: Optional path to save the generated workflow
      
      Returns:
          Generated DSL content and validation results
      
      Examples:
          generate_from_template("text2img_basic", {"prompt": "sunset"})
          generate_from_template("img2img", {"image_path": "input.png"}, "workflows/my_img2img.dsl")
      """
      try:
          # Validate template exists
          template = template_manager.get_template(template_name)
          if template is None:
              raise ToolError(f"Template '{template_name}' not found")
          
          # Validate parameters if provided
          if parameters:
              validation = template_manager.validate_parameters(template_name, parameters)
              if not validation["valid"]:
                  return {
                      "status": "error",
                      "errors": validation["errors"],
                      "warnings": validation.get("warnings", [])
                  }
          
          # Generate the workflow
          dsl_content = template_manager.generate_workflow(template_name, parameters)
          
          if dsl_content is None:
              raise ToolError(f"Failed to generate workflow from template '{template_name}'")
          
          result = {
              "status": "success",
              "template_name": template_name,
              "dsl_content": dsl_content,
              "parameters_used": parameters or {},
              "warnings": []
          }
          
          # Add warnings if any
          if parameters:
              validation = template_manager.validate_parameters(template_name, parameters)
              result["warnings"] = validation.get("warnings", [])
          
          # Save to file if requested
          if save_path:
              try:
                  path = validate_path(save_path)
                  path.write_text(dsl_content)
                  result["saved_to"] = str(path)
                  result["file_size"] = path.stat().st_size
              except Exception as e:
                  result["warnings"].append(f"Failed to save to {save_path}: {e}")
          
          return result
          
      except Exception as e:
          raise ToolError(f"Error generating from template: {e}")

• comfy_mcp/templates/manager.py:118-161 (helper)

  Core helper function in TemplateManager that implements the workflow generation logic by loading template DSL (custom or official), substituting parameters via string replacement, and returning the final DSL content.

  def generate_workflow(
      self, 
      template_name: str, 
      parameters: Optional[Dict[str, str]] = None,
      source: str = "auto"
  ) -> Optional[str]:
      """Generate a workflow DSL from template with parameter substitution."""
      # Try custom templates first, then official
      template = None
      dsl_content = None
      
      if source in ["auto", "custom"]:
          template = self.custom_templates.get(template_name)
          if template:
              dsl_content = template.dsl_content
      
      if not template and source in ["auto", "official"]:
          official_template = official_manager.get_template(template_name)
          if official_template and official_template.dsl_content:
              dsl_content = official_template.dsl_content
              # Create a minimal template-like object for parameter handling
              template = type('Template', (), {
                  'parameters': {},  # Official templates don't have default parameters
                  'dsl_content': dsl_content
              })()
      
      if not template or not dsl_content:
          return None
      
      # Start with template's default parameters
      final_params = template.parameters.copy() if hasattr(template, 'parameters') and template.parameters else {}
      
      # Override with provided parameters
      if parameters:
          final_params.update(parameters)
      
      # Substitute parameters in DSL content if any
      if final_params:
          for param_name, param_value in final_params.items():
              # Replace {param_name} with actual value
              placeholder = f"{{{param_name}}}"
              dsl_content = dsl_content.replace(placeholder, str(param_value))
      
      return dsl_content

• comfy_mcp/templates/manager.py:163-219 (helper)

  Helper function for parameter validation, extracts placeholders from DSL, checks required/missing/extra params, and performs type/constraint validation used by the tool handler.

  def validate_parameters(
      self, 
      template_name: str, 
      parameters: Dict[str, str],
      source: str = "auto"
  ) -> Dict[str, List[str]]:
      """Validate parameters for a template."""
      # Try to find template in custom or official
      template = None
      if source in ["auto", "custom"]:
          template = self.custom_templates.get(template_name)
      
      if not template and source in ["auto", "official"]:
          official_template = official_manager.get_template(template_name)
          if official_template and official_template.dsl_content:
              # Create minimal template object for validation
              template = type('Template', (), {
                  'parameters': {},
                  'dsl_content': official_template.dsl_content
              })()
      if not template:
          return {
              "valid": False,
              "errors": [f"Template '{template_name}' not found"],
              "warnings": []
          }
      
      errors = []
      warnings = []
      
      # Check for required parameters (those in template but not provided)
      template_params = template.parameters or {}
      required_params = set(self._extract_parameters_from_dsl(template.dsl_content))
      provided_params = set(parameters.keys())
      
      missing_params = required_params - provided_params
      if missing_params:
          errors.append(f"Missing required parameters: {', '.join(missing_params)}")
      
      # Check for extra parameters
      extra_params = provided_params - required_params
      if extra_params:
          warnings.append(f"Extra parameters will be ignored: {', '.join(extra_params)}")
      
      # Validate specific parameter types/constraints
      for param_name, param_value in parameters.items():
          if param_name in template_params:
              validation_errors = self._validate_parameter_value(
                  param_name, param_value, template_name
              )
              errors.extend(validation_errors)
      
      return {
          "valid": len(errors) == 0,
          "errors": errors,
          "warnings": warnings
      }

• comfy_mcp/mcp/server.py:31-41 (registration)

  Import and global initialization of TemplateManager instance used by all template tools including generate_from_template.

  from ..templates import TemplateManager
  
  # Create MCP server
  mcp = FastMCP("ComfyUI Workflow Manager 🎨")
  
  # Security: Define allowed base directory for file operations
  WORKFLOWS_BASE = Path.cwd() / "workflows"
  WORKFLOWS_BASE.mkdir(exist_ok=True)
  
  # Initialize template manager
  template_manager = TemplateManager()