appsgolem-mcp (Node / TypeScript)

An MCP server for the AppsGolem YouTube cutter API. It lets an AI agent (Claude Desktop, Claude Code, Cursor, …) cut clips from YouTube videos — in any format the web cutter supports — and get a direct download URL back. The REST logic lives in a small, dependency-light client (src/client.ts); src/server.ts is the thin MCP tool layer over it.

Get your API key → appsgolem.com/agents — sign up, add prepaid credits, and generate a key (ag_live_…). That page also has copy-paste setup for Claude Code, Codex, Cursor, and any MCP client, plus a prompt cookbook.

Requirements

• Node.js >= 18 (uses the global fetch).
• An AppsGolem API key (ag_live_…) — get one at appsgolem.com/agents (sign up → add credits → generate a key in your dashboard). Credits are prepaid; buy a pack or a subscription, no auto-renewal required.

Install / connect (no manual install)

npx fetches and runs the server on demand — nothing to install globally.

Claude Desktop / Cursor — add to the client's MCP config (e.g. claude_desktop_config.json):

{
  "mcpServers": {
    "appsgolem": {
      "command": "npx",
      "args": ["-y", "appsgolem-mcp"],
      "env": { "APPSGOLEM_API_KEY": "ag_live_…" }
    }
  }
}

Claude Code — one command:

claude mcp add appsgolem -e APPSGOLEM_API_KEY=ag_live_… -- npx -y appsgolem-mcp

The server speaks MCP over stdio (the transport those clients use). A missing APPSGOLEM_API_KEY is not fatal at startup — the server still starts and advertises its tools; each call then returns a clear config_error telling you to set the key.

Configuration

Env var	Required	Default	Notes
APPSGOLEM_API_KEY	yes	—	Your ag_live_… key.
APPSGOLEM_API_BASE	no	https://appsgolem.com	Override for self-host / dev.

Pricing

1 produced clip = 1 credit. 2160p (4K) = 4 credits per clip — except audio_only, which stays 1. A source longer than 2 h adds +1 once per job, but only when its duration is known (the surcharge is skipped if the probe can't determine it). A batch/stitch of N clips costs N per-clip. Failed cuts are never billed.

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Tools

The server exposes three tools. A call that passes MCP input-schema validation returns a structured result — the API's own JSON on success, or { "error": … } on any handler/API failure — and never raises a protocol-level error, so an agent always gets a usable object. (Invalid tool arguments are rejected by the MCP SDK before the handler runs, as a text-only isError result.)

1. cut_youtube_video

Cut a clip (or a batch of clips) from a YouTube video. By default it waits until the clip is produced and returns its status (including a download_url once a download token is ready); set wait: false to submit and return immediately with the current job (its state is normally queued after dispatch).

Parameters

Name	Type	Default	Notes
url	string	—	Required. YouTube watch / share / youtu.be URL. Playlists are rejected.
start	string	—	Clip start: "SS", "MM:SS", or "HH:MM:SS" (≤ 300 h). Omit when using clips.
end	string	—	Clip end, same formats (≤ 300 h). Omit when using clips.
resolution	string	1080p	144p · 240p · 360p · 480p · 720p · 1080p · 1440p · 2160p (4K; total cut ≤ 60 min).
mode	string	video	video · audio_only · both · nosound · short · gif · frames (see Modes below).
audio_format	string	—	The audio_only output format: mp3 · m4a · wav · flac (server defaults to mp3). both always produces MP3.
bitrate	string	—	Lossy-audio bitrate 320 · 256 · 192 · 128 (default 320): MP3/M4A in audio_only, MP3 in both; ignored for WAV/FLAC.
fast	boolean	false	Stream-copy (≈10× faster, keyframe-aligned); video / nosound / both only. Mutually exclusive with a non-1× speed — if both are set, fast wins and speed is forced to 1.0.
speed	number	1.0	Playback speed 0.5 · 1 · 1.25 · 1.5 · 2. video / nosound / both / audio_only.
interval_ms	integer	2000	frames sampling interval: 100 · 500 · 1000 · 2000 · 5000 · 10000 (non-sheet extraction is capped at 1,800 JPGs total across all clips).
burn_ts	boolean	false	frames: burn the source timestamp onto each JPG.
sheet	boolean	false	frames: return a single contact-sheet JPG (2–80 frames, single clip). Setting it disables burn_ts.
clips	array	—	An array of 1–10 { start, end } ranges instead of start/end (an empty array is rejected).
stitch	boolean	false	With 2+ clips, join them into one file (else a zip of clips); ignored for a single clip. video / audio_only / both / short / nosound.
idempotency_key	string	—	A stable key (≤ 200 chars) so a retried request reuses the same job (sent as the Idempotency-Key header).
wait	boolean	true	Poll until ready, up to the timeout_seconds polling deadline.
timeout_seconds	integer	300	Polling deadline in seconds (default 300). It bounds the polling only — the initial submission and one in-flight status request (each up to a 30 s request timeout) can extend total wall-clock.

Returns (wait: true, default) — the produced job status. download_url is present once a download token is available; if it isn't yet, poll again:

{
  "id": "e48db1a2-1c3d-4e5f-8a9b-0c1d2e3f4a5b",
  "state": "produced",
  "credits_reserved": 1,
  "created_at": "2026-08-22T12:00:00+00:00",
  "download_url": "https://appsgolem.com/v1/download/…/clip.mp4"
}

Returns (wait: false) — the job immediately, with its current state (normally queued after dispatch) and no download_url yet; poll get_cut_status with the id (or fetch poll_url):

{
  "id": "e48db1a2-1c3d-4e5f-8a9b-0c1d2e3f4a5b",
  "state": "queued",
  "credits_reserved": 1,
  "poll_url": "/v1/cuts/e48db1a2-1c3d-4e5f-8a9b-0c1d2e3f4a5b"
}

If the wait times out before the clip is ready, the result carries "still_processing": true and the job id — poll get_cut_status with that id. If the job reaches a terminal failure, the result is { "error": "cut_failed", "state": "failed" | "refunded", "id": … } (and no credit is charged).

2. get_cut_status

Check a cut job by its id. Use it to poll a job started with cut_youtube_video(wait=false) or one that timed out.

Name	Type	Notes
job_id	string	Required. The job id (a UUID) returned by cut_youtube_video.

Returns — the job's state; once produced/delivered it also carries a download_url when a download token is available (otherwise poll again):

{ "id": "e48db1a2-…", "state": "queued", "credits_reserved": 1, "created_at": "…" }

States progress accepted → queued → produced → delivered, or failed → refunded on error.

3. get_account_balance

Return the API account's spendable credit balance and current hourly cap. No parameters.

Returns

{ "balance": 412, "hourly_cap": 60 }

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Modes

mode	Output	Notable options
video	Video file, no watermark — normally MP4; fast preserves the source container (e.g. WebM at high res)	resolution, fast, speed
audio_only	mp3 / m4a / wav / flac	audio_format, bitrate, speed
both	Video + MP3 together, as a zip (fast may preserve the video's source container)	bitrate, fast, speed
nosound	Video with no audio track — normally MP4; fast preserves the source container	resolution, fast, speed
short	Portrait 9:16 — AI smart-crop when applicable, else a letterbox-blur fallback whose exact aspect depends on the source (Shorts / Reels / TikTok)	resolution
gif	Animated GIF (≤ 5 min; no multi-clip)	resolution
frames	JPG stills	interval_ms, burn_ts, sheet

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Example prompts

Because the agent picks the parameters from your request, you drive it in plain language:

• "Cut 0:30 to 1:15 from https://youtu.be/dQw4w9WgXcQ in 1080p." → cut_youtube_video(url, start="0:30", end="1:15")
• "Grab the audio of that video from 2:00 to 5:00 as an mp3." → mode="audio_only", audio_format="mp3"
• "Make a vertical short of the 10:00–10:45 highlight." → mode="short", start="10:00", end="10:45"
• "Turn 0:05–0:12 into a GIF." → mode="gif"
• "Extract a contact sheet of frames every 5 seconds from 1:00 to 2:00." → mode="frames", interval_ms=5000, sheet=true
• "Stitch 0:10–0:20 and 1:00–1:10 into one clip." → clips=[{start:"0:10",end:"0:20"},{start:"1:00",end:"1:10"}], stitch=true
• "Do a fast, stream-copy cut of 0:00–0:30." → fast=true
• "How many API credits do I have left?" → get_account_balance()

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Result & error shapes

Every result from a handler is a plain object (MCP argument-validation failures are the exception — see the Tools note above). On failure the object has an error code (the tool call still succeeds):

error	When
config_error	APPSGOLEM_API_KEY is missing.
invalid_api_key	The key was rejected (401).
invalid_job_id	job_id isn't a UUID.
not_found	No such job for this account (404).
cut_failed	The job reached failed/refunded (never billed).
network_error	Connection/transport failure or request timeout.
bad_request	The configured API base/path couldn't be built into a URL.
http_error	A ≥400 response whose JSON body isn't an { error: … } object (carries status).
bad_response	A success response whose body isn't a JSON object (array/scalar/null), or — with wait: true — a cut submission that came back without a usable job id.

API-level errors — validation 400, 402 insufficient_credits, 404 not_found, 409 idempotency_conflict / duplicate_in_flight, 429 rate_limited, and 503 rate_limiter_unavailable / database_busy — are returned as the API's own error body plus a status field. A 429 also includes retry_after (seconds, from Retry-After) plus a reason (submission_cap · request_rate · poll_rate) so an agent can tell which limit it hit and back off correctly. A 503 is usually transient (retry after a short delay), but a persistent 503 is a server-side problem to report — not to retry indefinitely.

Status polling is not rate-limited for normal use — checking a job's progress never counts against your submissions/hour cap. You never need to throttle get_cut_status yourself: cut_youtube_video(wait=true) polls and paces for you (honoring the server's poll_after cadence and any Retry-After), so a single tool call handles even long jobs.

Produced download links expire after a bounded window (~72 hours by default on appsgolem.com; configurable per deployment) — fetch the file within it.

A relative download_url (the API returns a path) is resolved to a full URL against the configured API base only when the result stays on that origin. Any download_url that resolves off the API's origin — an absolute URL to another host, or a relative path that escapes the origin — is dropped for safety: the field is removed and the result carries download_url_dropped: true, so you can tell it apart from a job that simply isn't produced yet. When cut_youtube_video is waiting for you (wait=true, the default), an off-origin link surfaces as a download_url_unsafe error instead of handing back a bad URL.

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Develop

npm install
npm run build      # tsc -> dist/
npm test           # builds, then runs node --test (no network)
npm start          # run the stdio server locally (key needed for calls, not startup)

Publishing

npm publish (from this directory) makes npx appsgolem-mcp work for everyone. The prepare script builds dist/ automatically on install/publish.