ComfyUI API Skill

Connect to ComfyUI's REST API to execute workflows, monitor progress, and retrieve outputs.

Configuration

Default URL

:

http://127.0.0.1:8188

Custom URL

Set in project manifest or pass as parameter

Timeout

30s for API calls, no timeout for generation polling

Two Modes

Online Mode (ComfyUI Running)

Full API access. Preferred mode for interactive work.

Test connection

:

GET /system_stats

Discover capabilities

Use

comfyui-inventory

skill

Queue workflow

:

POST /prompt

Poll for results

:

GET /history/{prompt_id}

every 5 seconds

Retrieve outputs

:

GET /view?filename=...

Offline Mode (No Server)

Export workflow JSON for manual loading in ComfyUI.

Generate workflow JSON following ComfyUI's format

Save to

projects/{project}/workflows/{name}.json

Instruct user to drag-drop into ComfyUI

API Operations

Check Server Status

curl

http://127.0.0.1:8188/system_stats

Response fields:

system.os

Operating system

system.comfyui_version

Version string

devices[0].name

GPU name

devices[0].vram_total

Total VRAM bytes

devices[0].vram_free

Free VRAM bytes

Queue a Workflow

curl

-X

POST http://127.0.0.1:8188/prompt

\

-H

"Content-Type: application/json"

\

-d

'{"prompt": WORKFLOW_JSON, "client_id": "video-agent"}'

WORKFLOW_JSON format:

{

"1"

:

{

"class_type"

:

"LoadCheckpoint"

,

"inputs"

:

{

"ckpt_name"

:

"flux1-dev.safetensors"

}

}

,

"2"

:

{

"class_type"

:

"CLIPTextEncode"

,

"inputs"

:

{

"text"

:

"photorealistic portrait..."

,

"clip"

:

[

"1"

,

1

]

}

}

}

Each node is keyed by a string ID. Inputs reference other nodes as

["{node_id}", {output_index}]

.

Response:

{

"prompt_id"

:

"abc-123-def"

,

"number"

:

1

}

Poll for Completion

curl

http://127.0.0.1:8188/history/abc-123-def

Incomplete

Returns

{}

(empty object)

Complete

Returns execution data with outputs:

{

"abc-123-def"

:

{

"outputs"

:

{

"9"

:

{

"images"

:

[

{

"filename"

:

"ComfyUI_00001.png"

,

"subfolder"

:

""

,

"type"

:

"output"

}

]

}

}

,

"status"

:

{

"completed"

:

true

}

}

}

Retrieve Output Image

curl

"http://127.0.0.1:8188/view?filename=ComfyUI_00001.png&subfolder=&type=output"

-o

output.png

Upload Reference Image

curl

-X

POST http://127.0.0.1:8188/upload/image

\

-F

"image=@reference.png"

\

-F

"subfolder=input"

\

-F

"type=input"

Cancel Current Generation

curl

-X

POST http://127.0.0.1:8188/interrupt

Free VRAM

curl

-X

POST http://127.0.0.1:8188/free

\

-H

"Content-Type: application/json"

\

-d

'{"unload_models": true}'

Polling Strategy

ComfyUI doesn't support WebSocket in CLI context. Use REST polling:

Queue workflow via

POST /prompt

→ get

prompt_id

Poll

GET /history/{prompt_id}

every

5 seconds

On empty response: generation in progress, continue polling

On populated response: check

status.completed

If

completed: true

, extract outputs

If error in status, route to

comfyui-troubleshooter

Timeout

Warn user after 10 minutes of polling. Video generation (Wan 14B) can take 15-30 minutes. Workflow Validation Before queuing any workflow: Read state/inventory.json (via comfyui-inventory ) For each node in workflow: verify class_type exists in installed nodes For each model reference: verify file exists in installed models Flag missing items with: Node: suggest ComfyUI-Manager install command Model: provide download link from references/models.md Version mismatch: suggest update Error Handling Error Cause Action Connection refused ComfyUI not running Switch to offline mode, save JSON 400 Bad Request Invalid workflow JSON Validate node connections 500 Internal Error ComfyUI crash Suggest restart, check logs Timeout (no response) Server overloaded Wait and retry once Reference Full API documentation: foundation/api-quick-ref.md