save_to_library
Idempotent
Save YouTube videos to your library using three modes: 'asr' bookmarks and marks as transcribed, 'summary' uploads a summary, 'both' does both. Idempotent updates.
Instructions
Save a video to the authenticated user's Library. Three modes via kind: 'asr' bookmarks the video and flips has_asr (use after a successful transcribe_video → fetch_transcript flow); 'summary' uploads a summary blob; 'both' does both at once. Idempotent: saving the same video twice updates the existing entry.
Input Schema
TableJSON Schema
| Name | Required | Description | Default |
|---|---|---|---|
| video_id | Yes | YouTube video ID (11 chars). | |
| kind | Yes | 'asr' (bookmark + flip has_asr), 'summary' (upload summary text), or 'both'. | |
| title | No | Video title (for display in the user's Library list). | |
| author | No | Channel / author name. | |
| thumbnail | No | Thumbnail URL. | |
| video_url | No | Full YouTube URL. | |
| language | No | Video language code (ISO 639-1). | |
| text | No | Summary text. REQUIRED when kind='summary' or kind='both'. Plain text or markdown — use the `format` param to declare which. | |
| locale | No | Summary locale (e.g. 'en', 'zh'). Used with kind='summary' or kind='both'. | |
| format | No | Summary format: 'markdown' (default) or 'text'. Use 'markdown' if your text contains **bold**, bullets, headings, or code fences so the web UI renders it; use 'text' for plain prose. | |
| model | No | Optional model identifier, e.g. 'claude-opus-4'. |
Implementation Reference
- src/index.js:294-355 (schema)Schema definition for save_to_library tool. Defines input parameters: video_id (required), kind (required, enum: asr/summary/both), title, author, thumbnail, video_url, language, text, locale, format, and model.
name: "save_to_library", description: "Save a video to the authenticated user's Library. Three modes via `kind`: 'asr' bookmarks the video and flips has_asr (use after a successful transcribe_video → fetch_transcript flow); 'summary' uploads a summary blob; 'both' does both at once. Idempotent: saving the same video twice updates the existing entry.", annotations: { title: "Save to Library", ...ANN.LIB_WRITE }, inputSchema: { type: "object", properties: { video_id: { type: "string", description: "YouTube video ID (11 chars).", minLength: 5, }, kind: { type: "string", description: "'asr' (bookmark + flip has_asr), 'summary' (upload summary text), or 'both'.", enum: ["asr", "summary", "both"], }, title: { type: "string", description: "Video title (for display in the user's Library list).", }, author: { type: "string", description: "Channel / author name.", }, thumbnail: { type: "string", description: "Thumbnail URL.", }, video_url: { type: "string", description: "Full YouTube URL.", }, language: { type: "string", description: "Video language code (ISO 639-1).", }, text: { type: "string", description: "Summary text. REQUIRED when kind='summary' or kind='both'. Plain text or markdown — use the `format` param to declare which.", }, locale: { type: "string", description: "Summary locale (e.g. 'en', 'zh'). Used with kind='summary' or kind='both'.", }, format: { type: "string", description: "Summary format: 'markdown' (default) or 'text'. Use 'markdown' if your text contains **bold**, bullets, headings, or code fences so the web UI renders it; use 'text' for plain prose.", enum: ["markdown", "text"], }, model: { type: "string", description: "Optional model identifier, e.g. 'claude-opus-4'.", }, }, required: ["video_id", "kind"], }, }, - src/index.js:408-441 (handler)Generic upstream call handler (callUpstream). The actual save_to_library logic is not implemented locally; all tool calls (including save_to_library) are forwarded to the upstream SubDownload MCP API via a JSON-RPC tools/call request.
async function callUpstream(name, args) { if (!API_KEY) { throw new Error( "SUBDOWNLOAD_API_KEY env var is not set. Get one at https://subdownload.com/account, then run with -e SUBDOWNLOAD_API_KEY=<your-key>." ); } const res = await fetch(UPSTREAM_URL, { method: "POST", headers: { "Content-Type": "application/json", Accept: "application/json, text/event-stream", Authorization: `Bearer ${API_KEY}`, }, body: JSON.stringify({ jsonrpc: "2.0", id: Date.now(), method: "tools/call", params: { name, arguments: args }, }), }); const text = await res.text(); let body; try { body = JSON.parse(text); } catch { throw new Error( `Upstream returned non-JSON response (HTTP ${res.status}): ${text.slice(0, 200)}` ); } if (body.error) { throw new Error(body.error.message || JSON.stringify(body.error)); } return body.result; } - src/index.js:73-406 (registration)Registration of all tools (including save_to_library) in the TOOLS array, which is served via ListToolsRequestSchema on line 448. The tool named 'save_to_library' is an entry in this array at index (lines 293-355).
const TOOLS = [ { name: "search_youtube", description: "Search YouTube globally for videos, channels, or playlists on any topic. Returns up to 50 results with metadata. Use this for topic-based discovery when the user has not specified a channel — for searching within a known channel use search_channel_videos instead.", annotations: { title: "Search YouTube", ...ANN.YT_READ }, inputSchema: { type: "object", properties: { q: { type: "string", description: "Search query (same syntax as YouTube's search bar, e.g. 'rust async tutorial', 'lex fridman dario amodei').", minLength: 1, }, type: { type: "string", description: "Search type: 'video', 'channel', or 'playlist'. Default: 'video'.", enum: ["video", "channel", "playlist"], }, limit: { type: "number", description: "Max results (1-50, default 20).", minimum: 1, maximum: 50, }, }, required: ["q"], }, }, { name: "fetch_video_info", description: "Fetch consolidated YouTube video metadata with numeric types — title, channel, duration, view count, publish date, thumbnail, description, captions availability. Does NOT include the transcript itself; call fetch_transcript or transcribe_video for that. Cheap, fast, free.", annotations: { title: "Fetch YouTube Video Info", ...ANN.YT_READ }, inputSchema: { type: "object", properties: { video_id: { type: "string", description: "11-char YouTube video ID (e.g. 'dQw4w9WgXcQ') or full URL (watch, youtu.be, shorts, embed, live).", minLength: 5, }, }, required: ["video_id"], }, }, { name: "fetch_transcript", description: "Fetch the existing official transcript (subtitles/captions) of a YouTube video, with per-segment timestamps and language detected. Errors with NO_CAPTIONS if the video has no captions — fall back to transcribe_video in that case to generate one with AI ASR. This call is free.", annotations: { title: "Fetch YouTube Video Transcript", ...ANN.YT_READ }, inputSchema: { type: "object", properties: { video_id: { type: "string", description: "YouTube video ID (e.g. 'dQw4w9WgXcQ') or full YouTube URL.", minLength: 5, }, lang: { type: "string", description: "ISO 639-1 language code to select among multilingual captions (e.g. 'en', 'zh', 'ja'). Omit for the video's default language.", }, save: { type: "boolean", description: "When true, also save the video to the user's Library in the same call. Bookmarks the meta row and flips has_asr when the transcript was produced by our ASR. Does NOT upload a summary — use save_to_library with kind='summary' or kind='both' for that.", }, }, required: ["video_id"], }, }, { name: "transcribe_video", description: "Start an asynchronous AI ASR (Whisper) transcription of a YouTube video. Returns immediately with a task_id and estimated_wait_seconds; the actual transcription runs in the background. Poll status with get_asr_task. Use this when fetch_transcript returned NO_CAPTIONS or when the video has no captions. Costs 5 credits, debited only on successful completion.", annotations: { title: "Transcribe YouTube Video (Async)", ...ANN.ASR_START }, inputSchema: { type: "object", properties: { video_url: { type: "string", description: "YouTube URL (watch, youtu.be, shorts, or embed form). Full URL preferred.", minLength: 5, }, lang: { type: "string", description: "Optional language hint (ISO 639-1, e.g. 'en', 'zh'). Omit to auto-detect.", }, }, required: ["video_url"], }, }, { name: "get_asr_task", description: "Poll the status of an ASR task created by transcribe_video. Returns one of `queued`, `downloading`, `transcribing`, `finalizing`, `done`, or `failed`. When status is `done`, includes the full transcript with timestamps. Recommended polling interval: 3-5 seconds. Free — does not consume credits.", annotations: { title: "Get ASR Task Status", ...ANN.ASR_POLL }, inputSchema: { type: "object", properties: { task_id: { type: "string", description: "Task ID returned by transcribe_video.", minLength: 1, }, }, required: ["task_id"], }, }, { name: "resolve_channel", description: "Resolve a YouTube @handle, channel URL, video URL, or raw channel ID into canonical channel info (channel ID, name, handle, subscriber count, video count, avatar). Call this first when you only have a handle or URL but need a channel ID for the other channel-scoped tools.", annotations: { title: "Resolve YouTube Channel", ...ANN.YT_READ }, inputSchema: { type: "object", properties: { input: { type: "string", description: "@handle (e.g. '@MrBeast'), channel URL, video URL, or UC... channel ID. All common forms are accepted.", minLength: 1, }, }, required: ["input"], }, }, { name: "list_channel_videos", description: "List all videos from a YouTube channel ordered by publish date (newest first), with pagination. Returns up to 30 per page plus a `continuation` token if more results exist. For just the most recent handful, prefer get_channel_latest_videos for simplicity.", annotations: { title: "List Channel Videos", ...ANN.YT_READ }, inputSchema: { type: "object", properties: { channel: { type: "string", description: "@handle, channel URL, or UC... channel ID. Required for the first page; omit on subsequent pages and pass `continuation` instead.", }, continuation: { type: "string", description: "Pagination token from a previous response's `continuation` field. Omit for the first page.", }, }, }, }, { name: "get_channel_latest_videos", description: "Get the most recent videos from a YouTube channel — convenience wrapper over list_channel_videos with no pagination. Best for 'what did this creator publish recently?' style queries.", annotations: { title: "Get Channel Latest Videos", ...ANN.YT_READ }, inputSchema: { type: "object", properties: { channel: { type: "string", description: "@handle (e.g. '@mkbhd'), channel URL, or UC... channel ID.", minLength: 1, }, }, required: ["channel"], }, }, { name: "search_channel_videos", description: "Search for specific videos within a single YouTube channel. Restricts results to the given channel. Use after resolve_channel if starting from a handle. Useful for 'find Karpathy's video about backpropagation' style queries.", annotations: { title: "Search Channel Videos", ...ANN.YT_READ }, inputSchema: { type: "object", properties: { channel: { type: "string", description: "@handle, channel URL, or UC... channel ID.", minLength: 1, }, q: { type: "string", description: "Search query (matched against video title and description within the channel).", minLength: 1, }, limit: { type: "number", description: "Max results (1-50, default 30).", minimum: 1, maximum: 50, }, }, required: ["channel", "q"], }, }, { name: "list_playlist_videos", description: "List videos in a YouTube playlist in order, with pagination. Returns video metadata and position within the playlist. Works for any public or unlisted playlist exposed by its URL/ID.", annotations: { title: "List Playlist Videos", ...ANN.YT_READ }, inputSchema: { type: "object", properties: { playlist: { type: "string", description: "Playlist URL or ID (typically starts with 'PL', 'UU', 'LL', or 'FL'). Required for the first page.", }, continuation: { type: "string", description: "Pagination token from a previous response's `continuation` field. Omit for the first page.", }, }, }, }, { name: "save_to_library", description: "Save a video to the authenticated user's Library. Three modes via `kind`: 'asr' bookmarks the video and flips has_asr (use after a successful transcribe_video → fetch_transcript flow); 'summary' uploads a summary blob; 'both' does both at once. Idempotent: saving the same video twice updates the existing entry.", annotations: { title: "Save to Library", ...ANN.LIB_WRITE }, inputSchema: { type: "object", properties: { video_id: { type: "string", description: "YouTube video ID (11 chars).", minLength: 5, }, kind: { type: "string", description: "'asr' (bookmark + flip has_asr), 'summary' (upload summary text), or 'both'.", enum: ["asr", "summary", "both"], }, title: { type: "string", description: "Video title (for display in the user's Library list).", }, author: { type: "string", description: "Channel / author name.", }, thumbnail: { type: "string", description: "Thumbnail URL.", }, video_url: { type: "string", description: "Full YouTube URL.", }, language: { type: "string", description: "Video language code (ISO 639-1).", }, text: { type: "string", description: "Summary text. REQUIRED when kind='summary' or kind='both'. Plain text or markdown — use the `format` param to declare which.", }, locale: { type: "string", description: "Summary locale (e.g. 'en', 'zh'). Used with kind='summary' or kind='both'.", }, format: { type: "string", description: "Summary format: 'markdown' (default) or 'text'. Use 'markdown' if your text contains **bold**, bullets, headings, or code fences so the web UI renders it; use 'text' for plain prose.", enum: ["markdown", "text"], }, model: { type: "string", description: "Optional model identifier, e.g. 'claude-opus-4'.", }, }, required: ["video_id", "kind"], }, }, { name: "list_library", description: "List videos the user has saved to their Library (transcripts + summaries). Supports substring search on title/author, favorites filter, and pagination. Returns recently saved items first. Scoped to the calling user's data only.", annotations: { title: "List Saved Library", ...ANN.LIB_READ }, inputSchema: { type: "object", properties: { favorite: { type: "boolean", description: "When true, return only items the user has favorited.", }, q: { type: "string", description: "Substring match on title and author.", }, limit: { type: "number", description: "Max items per page (1-100, default 20).", minimum: 1, maximum: 100, }, offset: { type: "number", description: "Pagination offset (number of items to skip).", minimum: 0, }, }, }, }, { name: "get_library_item", description: "Read a saved Library item with its transcript and AI summary inline (when available). Use after list_library to fetch the full content the user saved. Free.", annotations: { title: "Get Library Item", ...ANN.LIB_READ }, inputSchema: { type: "object", properties: { id: { type: "number", description: "Library item id (returned by list_library or save_to_library).", }, locale: { type: "string", description: "Summary locale to fetch (e.g. 'en', 'zh'). Defaults to 'en'.", }, }, required: ["id"], }, }, ]; - src/index.js:448-462 (helper)Request handlers. ListToolsRequestSchema returns the TOOLS array (registration). CallToolRequestSchema forwards all tool invocations to the upstream API via callUpstream, which is the actual handler.
server.setRequestHandler(ListToolsRequestSchema, async () => ({ tools: TOOLS })); server.setRequestHandler(CallToolRequestSchema, async (request) => { try { return await callUpstream( request.params.name, request.params.arguments || {} ); } catch (err) { return { content: [{ type: "text", text: err.message || String(err) }], isError: true, }; } });