comfy-native-apps

A 6-tool MCP server that drives only ComfyUI's native .app.json apps (the built-in "构建应用 / Build App" feature) and manages the render queue. It does the UI→API conversion itself and uses only ComfyUI's stable core HTTP API, so it works against a headless OR a frontend ComfyUI — with zero dependency on the artokun comfyui-mcp / panel plugin.

Node 18+ only (global fetch, structuredClone). No npm install.

Why

artokun's comfyui-mcp exposes ~38 action-parameterized tools (plus 3 facade meta-tools and a 96-tool panel surface). Even its compact mode forces a list → describe_tool → call_tool chain that a 9B-class local model loops on describe_tool forever. This server deletes the indirection: the model sees exactly six single-purpose tools.

Related MCP server: ComfyUI MCP Server

Tools

run_app app may be the number from list_apps, the app name, or its id (relative workflows path). values keys are the friendly param labels (prompt, seed, …). A seed of -1 rolls a random seed.

How a native app is read

A .app.json wraps its whole graph in one subgraph. This server reads the declared I/O from definitions.subgraphs[0].inputs[] / .outputs[] (each port has a label, type, and a linkIds that points at the internal node+widget to fill). It then converts the subgraph's nodes + links to an API-format prompt:

• a socket linked from a real internal node → [String(nodeId), slot]

• a socket linked from the inputNode shell (-10) or not linked → its widgets_values_named default

• a model-filled value → the override (type-coerced to the port's declared type)

• widgets that aren't sockets (e.g. KSampler control_after_generate) → appended so the prompt is complete

• a synthetic SaveImage / SaveAnimatedWEBM is attached to each IMAGE/VIDEO output so the result is saved and fetched via /view

Where a port's real value lives. In app mode the exposed input ports' configured values are stored on the subgraph reference node — the top-level node whose type is the subgraph's id — in its widgets_values_named, keyed by port name. The internal nodes (e.g. a UNETLoader) keep the template's original defaults, which can be stale. This server reads the port values from the reference node and applies them to the internal node+socket each port feeds (as pre-populated overrides), so the app runs with the values the user actually set — including model paths with their subfolder prefix (e.g. zimage\z_image_turbo_int8_convrot.safetensors). User run_app values layer on top.

Because the conversion happens here, the same run_app works whether ComfyUI is headless (--front-end-version 0, no UI) or running the web frontend — only the core API is touched. The .app.json files are read straight off disk.

Config (env vars)

Client config (Claude Code / any MCP client)

{
  "command": "node",
  "args": ["E:/AIGenerationStudio/tools/comfy-native-apps/comfy_native_apps.mjs"],
  "env": { "COMFYUI_PORT": "8188" }
}

Wired into this workspace's .mcp.json as the server comfy-native-apps.

Files

• comfy_native_apps.mjs — the MCP stdio server (6 tools, newline-delimited JSON-RPC 2.0)

• native_lib.mjs — workflows discovery, app loading, UI→API conversion, HTTP, queue

• drive_safe.mjs — non-destructive end-to-end test (list_apps + run_app + job_status)

Note on models

An app's default model names must exist on the target machine. If an app was built with a model that isn't installed, run_app returns ComfyUI's value_not_in_list error naming the missing file; override the *_name params to an installed model.