ComfyUI MCP Server

Instructions

Implementation Reference

• src/tools/generation.ts:9-62 (handler)

  Core implementation of the comfy_submit_workflow tool handler. Parses input workflow JSON, validates it, applies optional parameter overrides, submits to ComfyUI API, and returns prompt_id, queue position, and status.

  export async function handleSubmitWorkflow(input: SubmitWorkflowInput) {
    try {
      const client = getComfyUIClient();
      const processor = new WorkflowProcessor();
  
      // Parse workflow
      const workflow = processor.parseWorkflow(input.workflow);
  
      // Validate workflow
      if (!validateWorkflowJSON(workflow)) {
        throw ComfyUIErrorBuilder.invalidWorkflow('Invalid workflow structure');
      }
  
      // Apply overrides
      const modifiedWorkflow = await processor.applyOverrides(workflow, input.overrides);
  
      // Submit to ComfyUI
      const response = await client.submitWorkflow(modifiedWorkflow, input.client_id);
  
      return {
        content: [{
          type: "text",
          text: JSON.stringify({
            prompt_id: response.prompt_id,
            number: response.number,
            status: response.node_errors ? "failed" : "queued",
            message: response.node_errors
              ? "Workflow validation failed"
              : `Workflow queued successfully at position ${response.number}`,
            node_errors: response.node_errors
          }, null, 2)
        }]
      };
    } catch (error: any) {
      if (error.error) {
        // Already a ComfyUIError
        return {
          content: [{
            type: "text",
            text: JSON.stringify(error, null, 2)
          }],
          isError: true
        };
      }
  
      return {
        content: [{
          type: "text",
          text: JSON.stringify(ComfyUIErrorBuilder.executionError(error.message), null, 2)
        }],
        isError: true
      };
    }
  }

• src/types/tools.ts:4-28 (schema)

  Zod input schema for the tool, defining workflow (JSON string or object), optional overrides for common parameters like prompts, seed, dimensions, LoRAs, and optional client_id.

  export const SubmitWorkflowSchema = z.object({
    workflow: z.union([z.string(), z.record(z.any())]),
    overrides: z.object({
      positive_prompt: z.string().optional(),
      negative_prompt: z.string().optional(),
      seed: z.number().int().optional(),
      steps: z.number().int().min(1).max(150).optional(),
      cfg: z.number().min(0).max(30).optional(),
      sampler_name: z.string().optional(),
      scheduler: z.string().optional(),
      width: z.number().int().min(64).max(8192).optional(),
      height: z.number().int().min(64).max(8192).optional(),
      denoise: z.number().min(0).max(1).optional(),
      input_image: z.string().optional(),
      batch_size: z.number().int().min(1).max(100).optional(),
      model: z.string().optional(),
      vae: z.string().optional(),
      lora: z.array(z.object({
        name: z.string(),
        strength_model: z.number(),
        strength_clip: z.number()
      })).optional()
    }).optional(),
    client_id: z.string().optional()
  });

• src/server.ts:68-70 (registration)

  Tool metadata registration in the ListTools response, including name, description, and derived JSON input schema.

  name: 'comfy_submit_workflow',
  description: 'Submit a complete workflow JSON to ComfyUI for execution. Supports parameter overrides for dynamic modifications without editing the workflow structure.',
  inputSchema: zodToJsonSchema(SubmitWorkflowSchema) as any,

• src/server.ts:149-150 (registration)

  Handler dispatch in the CallToolRequest switch statement, routing tool calls to the handleSubmitWorkflow function.

  case 'comfy_submit_workflow':
    return await handleSubmitWorkflow(args as any);