CapCut from Claude

The CapCut MCP was built for Codex. This skill is the Claude adaptation: the official material is kept verbatim under official/ (plugin v0.2.6), and this file states how to use it here, plus what was verified in real use (2026-10-26/27, Claude desktop Code tab, Windows).

Paths below are relative to this skill's folder (~/.claude/skills/capcut/).

If official/ is missing (fresh clone), run python scripts/fetch_official.py first — it downloads CapCut's plugin bundle from CapCut's CDN (the official material is not redistributed in this repo). --force refreshes it to the latest published version.

0. Connection (do this first if tools are missing or failing)

The only working way to connect is local MCP servers in the Claude desktop config, via mcp-remote. Adding CapCut as a claude.ai custom connector does NOT work: CapCut's OAuth server rejects Claude's dynamic client registration ("无法在 CapCut 的登录服务中注册"), and a client ID cannot be supplied.

%LOCALAPPDATA%\Claude-Data\<profile>\claude_desktop_config.json (or %APPDATA%\Claude\claude_desktop_config.json) → mcpServers:

"capcut":          {"command": "cmd", "args": ["/c", "npx", "-y", "mcp-remote", "https://www.capcut.com/api/external_mcp"]},
"capcut_resource": {"command": "cmd", "args": ["/c", "npx", "-y", "mcp-remote", "https://www.capcut.com/api/external_mcp/resource"]}

• capcut = account-bound tools (OAuth). capcut_resource = identity-free card tools (no login). Back up the config before editing; the user must fully quit and reopen Claude after editing.

Setup from scratch (no mcp__capcut__* tools in the session):

1. Check prerequisites: node --version (≥14) and npx on PATH.
2. Find the live config: search %LOCALAPPDATA%\Claude-Data\*\claude_desktop_config.json first, then %APPDATA%\Claude\claude_desktop_config.json. Read it, copy it to claude_desktop_config.json.bak-<date>, add the two entries under mcpServers (create the key if absent) without touching anything else, and re-parse the file as JSON to confirm it's valid.
3. Ask the user to sign the system default browser into the CapCut account the drafts should live in, then fully quit Claude (tray icon → Quit) and reopen it.
4. On start, mcp-remote opens the CapCut authorize page in that browser; the user approves (an instant flash-and-close means it auto-approved — fine).
5. The current session cannot see servers added after it started: continue in a new Code-tab session. Verify there with start_stdraft_session (should return a session_id) and search_capcut_material (type: music).
6. Optional: sign Claude's built-in browser into the same CapCut account so drafts can be inspected there.

• OAuth tokens are cached in ~/.mcp-auth/mcp-remote-v1/<hash>_tokens.json and <hash>_client_info.json.
• Re-authorize / switch account: ask the user first; delete those two files; the user signs the system default browser into the desired CapCut account (same login method — Google/email/TikTok are different accounts) before restarting; then fully quit and reopen Claude; mcp-remote opens the CapCut authorize page (it may flash and close if that browser is already signed in — that is success). Verify with start_stdraft_session.
• Symptom get user workspace failed: check login error on every call = the cached grant is dead → re-authorize as above.
• Re-authorizing logs the same account out of other CapCut web sessions (including Claude's built-in browser); the user must sign in there again.
• Drafts are saved into whichever account the MCP is authorized as. If the user can't see a draft, compare accounts first.

1. Which surface works

Cards (capcut_resource: templates_preview_v2, editing_plan, video_preview, background_music, billing_confirmation) are fetched but not rendered in the Code tab — results arrive as text/JSON. Never wait on a card; read the data and present it yourself.

2. Official docs to read (only what the task needs)

Must-read for any draft work: official/capcut-stdraft-builder/reference/application.md (function contracts). Everything else only when the task touches it.

Ignore Codex-only parts: codex plugin install/upgrade, codex app-server/capcut-login.mjs OAuth, "New-Task Handoff"/fork, require_escalated sandbox flags, TTY ticket entry, "end the turn silently after a card".

3. Core workflow: build/edit a cloud draft

Shell: run commands in the Bash tool (Git Bash), not PowerShell. Use forward-slash Windows paths (D:/proj/clip.mp4) or single-quoted ones. Work in the user's project folder (e.g. <project>/capcut_work/) so upload maps and drafts survive the session.

1. Upload local media with the official uploader only (never hand-rolled VOD code):
   • capcut_asset_upload_credential with version: 2 and files: [{file_name, size_bytes}] for the whole batch → upload_ticket (a short-lived single-batch capability; it necessarily passes through this conversation once — never log it elsewhere).
   • Write the ticket with no trailing-newline issues, pipe it on stdin (never in argv), delete the file:

     cd <project>/capcut_work && printf '%s\n' '<ticket>' > ticket.tmp
     node ~/.claude/skills/capcut/official/capcut-upload/scripts/capcut-upload.mjs \
       --files '[{"client_id":"c1","file":"D:/proj/a.mp4"},{"client_id":"c2","file":"D:/proj/b.mp3"}]' \
       --upload-ticket-stdin --json < ticket.tmp > upload_result.json 2> upload_stderr.txt; rm -f ticket.tmp

     (single file: --file <path> --client-id c1; progress → stderr, JSON → stdout.)
   • Success = non-empty vid and setPublic.success:true. Save a name → {vid, duration} map (upload_map.json); never re-upload items that already have a vid. Tickets expire in ~1 h.
2. Session: start_stdraft_session once per draft; keep session_id. Before each edit round call check_stdraft_state(session_id, local_package_id):
   • brand-new draft: pass ""; expect server_package_id:"" → build from scratch and push with base_package_id:"";
   • otherwise follow the baseline table in official/web-collaborative-editing/SKILL.official.md (stale → get_stdraft_snapshot first).
3. Build locally with the official atomic functions (Python ≥3.8, stdlib only, run with python -B, sys.path.insert(0, "C:/Users/<user>/.claude/skills/capcut/official/capcut-stdraft-builder/scripts")): apply_video, apply_audio, apply_text, apply_text_template, apply_captions, apply_video_effect, apply_filter, apply_transition, update_material, update_placement, update_caption_text, remove_material, unset_attribute. Chain result["draft"]. New draft root: {"version":"0.1.0","segments":[{"id":"draft","type":"DRAFT","attributes":{"width":1920,"height":1080,"ratio_type":"16:9"}}]}.
   • Mute a clip: apply_video(..., volume=0.0). Times are integer ms.
   • SOURCE_RANGE_UNVERIFIED is raised for every vid/sid source — expected. Check it yourself: source_start_ms + duration_ms × speed must not exceed the source length (from upload_map.json, or duration_ms in the music search result).
   • Picking search results: prefer an item whose duration_ms covers the needed length and whose title/caption fits the mood; say which one you chose.
4. Prepare the push: python -B ~/.claude/skills/capcut/scripts/draft_tool.py slim draft.json draft_slim.json (short ids, one segment per line, re-validated, warns over ~60k chars). Read draft_slim.json and paste its full text verbatim as stdraft_json in push_stdraft_snapshot (this costs its size in tokens twice — keep drafts lean).
5. After push: if the result was saved to a file by the harness, run draft_tool.py summary <file> / urls <file>; if it came back inline, save it to push_result.json first (or pipe it: ... summary -). Give the user web_editor_url as a Markdown link labelled with web_editor_text verbatim (server-localized, may be e.g. "Buksan sa CapCut"). Use the returned stdraft_json/server_package_id as the next baseline.
   • Normal server rewrites (not errors): vid:// → asset://<id>; DRAFT gets a random id and loses ratio_type; layers are renumbered; end.ms is added everywhere; TEXT gets font_color/line_max_width and a PATCH child ("style copy"); VIDEO gets crop/background.* defaults; AUDIO meta_type becomes lowercase. Compare content, timing, volume, speed, transitions and keyframes — not ids or layer numbers.
6. Optionally open embed_editor_url in the built-in browser to look; it only works if that browser is signed into the same CapCut account. Large projects take 30–60 s to load; text may only draw after a segment is selected.

Push pitfalls (verified)

• Timeout ≠ failure. First push into a new account copies every media file and can exceed the client timeout while still succeeding. Never blindly re-push: check_stdraft_state first; if a version now exists, get_stdraft_snapshot (summarise via draft_tool) and continue from it. A blind re-push returns STDRAFT_VERSION_CONFLICT.
• A draft created by a timed-out push may not show in the Library and returns no URL; one more push on top of it (same content, correct base) returns the editor URLs.
• Size: ~55k chars pushed reliably; ~90k did not fit in one call. Keep pushes lean (drop optional keyframes/styles, add them in the web editor).

4. Verified capability boundaries

Works and survives cloud save: video clips (source in-point, duration, volume, speed), transitions (add/replace/remove; same layer, contiguous), music & sound effects (sid:// from search or own vid://; volume; no auto-loop), filters with intensity, plain text (font, size, colour, position, border), font swap, text effects (flower), text templates (server adds an IN animation; slot count unverifiable), captions with word timing and update_caption_text, remove/unset, placement/layer/timing changes, scale_*/alpha keyframes on clips with speed 1.

Lost or broken on save:

• VIDEO_EFFECT segments (video effects and face effects) are dropped entirely — tell the user to add effects in the web editor.
• Keyframes on clips whose speed ≠ 1 get their times rescaled by the speed and are mostly dropped.
• Anything the builder doesn't cover (masks, stickers, curves, grading) must be done in the web editor.
• Export/render is not available through the MCP: the user exports in the CapCut editor.

Materials search: music, sound_effect, video_effect honour the prompt; font, text_effect, text_template, face_effect, transition, filter return a fixed curated list (max 20) regardless of prompt — there is no plain cross-dissolve; curated fonts are Latin (Chinese falls back to the default font vimo://7317175475195875841, which renders CJK). Video footage/images are not searchable — upload them.

Automatic captions (auto_caption_submit / auto_caption_query): speech recognition only; Pro membership needed (free accounts get PAYWALL_REQUIRED — show benefit_check_label link verbatim). Useless for song lyrics (a whole song returned one garbage line) — use local Whisper + known lyrics for lyric timing instead.

Template search: capcut_template_search → poll capcut_template_search_poll_v2 until terminal → templates_preview_v2(search_id) returns the template data (card not rendered; list title, duration, usage and page_url for the user). Relevance is loose; results persist 15 days; max 10.

AI rough cut (AI Lab): capcut_ailab_start_edit(assets=[{resource_id: <vid>, file_name}], query) → poll → a plan event arrives with status loop_turn_completed; relay the plan to the user, then capcut_ailab_submit_plan_response without card_id (the plan's event id is rejected as plan_card_id_invalid) and with the user's exact choice text. Music and final-video events follow (~2 min for a 10 s cut). Call video_preview with the final event's context/resources unchanged to get the result's editable STDraft (stdraft field) — import it into a draft session to keep editing. Audio-only assets are rejected (unsupported_edit_file_name). Do not use AI Lab for caption-only requests.

Image/video generation (Seedream / Seedance): spends credits. Cards don't render here, so: submit with confirmed:false (no unique_key) → on CONFIRMATION_REQUIRED tell the user the exact credits_amount → only after the user explicitly approves that amount in chat, retry with confirmed:true and the returned unique_key/same generate_id. Never confirm on the user's behalf. Poll capcut_generation_poll until next_action=none, then generation_result(task_id) and report actual_credits. (Not yet exercised end-to-end.)

5. Delivery rules

• Every successful push: summarise what changed and what the server dropped, then end with the web_editor_url link.
• State unverified things as unverified (e.g. "preview not checked visually").
• Keep upload maps, draft JSON and helper outputs in the project folder, not only in a temp dir, so later sessions can continue.
• Leftover test drafts live in the user's CapCut Library; mention them so the user can delete them.