openclip-captions

OpenClip: captions on clips

render_clip burns animated captions into a viral moment produced by the OpenClip clipping pipeline. This is part of the PAID pipeline, it needs an active subscription and credits.

Captions here are rendered into the video, not a sidecar subtitle file. If the user wants an SRT or VTT file instead, that is the free transcribe tool, see openclip-transcription.

Setup (once)

OpenClip is a remote MCP server at https://openclip.app/mcp. Sign in with your OpenClip account when the OAuth prompt appears, there is no API key to copy.

• Claude Code: claude mcp add --transport http openclip https://openclip.app/mcp, then /mcp to authorize.
• Claude Desktop / web: Settings, Connectors, "Add custom connector", paste the URL, sign in.
• Cursor (.cursor/mcp.json): { "mcpServers": { "openclip": { "url": "https://openclip.app/mcp" } } }
• Header-only clients: mint an MCP token at openclip.app/settings/connect and connect to https://openclip.app/mcp/key with Authorization: Bearer <token>.

Sanity check: call get_account and confirm credits_remaining > 0.

The loop

1. Have a moment. You need a moment_id from list_clips(job_id). If the user has not run a video through the pipeline yet, start with submit_video, see the openclip-clipping skill.
2. Pick a preset. Call list_caption_presets to get the current keys. Known keys: default, dan, dan-reveal, pop, mozi, kendrick, sara, lucy, tayo, beast. Always confirm with the call, keys can change. That same call also returns the full caption-style property schema and the caption position options, which is what you need for custom styling rather than a named preset.
3. Render. render_clip(moment_id, caption_preset).
4. Poll. Rendering is async. Poll list_clips(job_id) and watch that moment's rendered_clip field. When it appears it holds {url, size_bytes}, the finished captioned video. get_render_status reports on the render directly.

Choosing a preset

Presets are visual styles, not just fonts. When the user names a creator or a vibe, map it:

• Big, punchy, word-by-word pop with heavy outline - beast.
• Clean and readable, safe default for a brand account - default.
• Bouncy and playful - pop.
• Reveal-style where words appear progressively - dan-reveal.

When the user does not care, use default and show them the other keys so they can swap. When they want something no preset covers, pull the caption-style property schema from list_caption_presets and build a custom style instead of forcing a near-miss preset.

Rules

• Always confirm preset keys with list_caption_presets before rendering. An unknown caption_preset comes back as a validation message on the tool result.
• Always poll. render_clip returns immediately, the video is not ready yet.
• A moment can be re-rendered with a different preset. rendered_clip reflects the latest successful render.
• clip is the unrendered cut, clip_watermarked is the watermarked version, rendered_clip is the captioned output. Hand the user the right one.
• Times are milliseconds.

Errors

Tool failures come back as a tool result with isError: true and a plain-text message, not an HTTP status.

• "Viral moment not found." - the moment_id is wrong or belongs to another account. Re-fetch with list_clips and use an id from that response.
• "Not authenticated. Reconnect your OpenClip token." - reconnect or re-mint the token.
• An unknown preset key returns the validation message text. Call list_caption_presets and retry with a real key.

Example prompts to actions

• "Add captions to that clip" - list_caption_presets, render_clip(moment_id, caption_preset="default"), poll.
• "Make it look like MrBeast" - render_clip(moment_id, caption_preset="beast"), poll.
• "What caption styles are there?" - list_caption_presets, show the keys.
• "Caption all the top 3" - list_clips, take the top 3 by virality_score, render_clip each, poll until every rendered_clip is present.
• "I want the captions at the top in my brand font" - list_caption_presets for the style schema and position options, then render with a custom style.

Related

Producing the clips to caption is openclip-clipping. Standalone SRT and VTT subtitle files are openclip-transcription. Locking a caption preset into a reusable processing agent is covered in openclip-clipping.