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Free Caption Generator

by peandrover adam · GitHub ↗ · v1.0.0 · MIT-0
cross-platform ⚠ suspicious
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Install in OpenClaw
/install free-caption-generator
Description
Turn a 3-minute YouTube tutorial video into 1080p captioned video files just by typing what you need. Whether it's adding subtitles to social media and YouTu...
README (SKILL.md)

Getting Started

Got video files to work with? Send it over and tell me what you need — I'll take care of the AI caption generation.

Try saying:

  • "add a 3-minute YouTube tutorial video into a 1080p MP4"
  • "add captions in English and Spanish"
  • "adding subtitles to social media and YouTube videos for content creators"

Getting Connected

Before handling any user request, establish a connection to the backend API. Show a brief status like "Connecting...".

If NEMO_TOKEN is in the environment, use it directly and create a session. Otherwise, acquire a free starter token:

  • Generate a UUID as client identifier
  • POST to https://mega-api-prod.nemovideo.ai/api/auth/anonymous-token with the X-Client-Id header
  • The response includes a token with 100 free credits valid for 7 days — use it as NEMO_TOKEN

Then create a session by POSTing to https://mega-api-prod.nemovideo.ai/api/tasks/me/with-session/nemo_agent with Bearer authorization and body {"task_name":"project","language":"en"}. The session_id in the response is needed for all following requests.

Tell the user you're ready. Keep the technical details out of the chat.

Free Caption Generator — Add Captions to Videos Automatically

Drop your video files in the chat and tell me what you need. I'll handle the AI caption generation on cloud GPUs — you don't need anything installed locally.

Here's a typical use: you send a a 3-minute YouTube tutorial video, ask for add captions in English and Spanish, and about 30-60 seconds later you've got a MP4 file ready to download. The whole thing runs at 1080p by default.

One thing worth knowing — shorter clips under 5 minutes generate captions significantly faster.

Matching Input to Actions

User prompts referencing free caption generator, aspect ratio, text overlays, or audio tracks get routed to the corresponding action via keyword and intent classification.

User says... Action Skip SSE?
"export" / "导出" / "download" / "send me the video" → §3.5 Export
"credits" / "积分" / "balance" / "余额" → §3.3 Credits
"status" / "状态" / "show tracks" → §3.4 State
"upload" / "上传" / user sends file → §3.2 Upload
Everything else (generate, edit, add BGM…) → §3.1 SSE

Cloud Render Pipeline Details

Each export job queues on a cloud GPU node that composites video layers, applies platform-spec compression (H.264, up to 1080x1920), and returns a download URL within 30-90 seconds. The session token carries render job IDs, so closing the tab before completion orphans the job.

Base URL: https://mega-api-prod.nemovideo.ai

Endpoint Method Purpose
/api/tasks/me/with-session/nemo_agent POST Start a new editing session. Body: {"task_name":"project","language":"\x3Clang>"}. Returns session_id.
/run_sse POST Send a user message. Body includes app_name, session_id, new_message. Stream response with Accept: text/event-stream. Timeout: 15 min.
/api/upload-video/nemo_agent/me/\x3Csid> POST Upload a file (multipart) or URL.
/api/credits/balance/simple GET Check remaining credits (available, frozen, total).
/api/state/nemo_agent/me/\x3Csid>/latest GET Fetch current timeline state (draft, video_infos, generated_media).
/api/render/proxy/lambda POST Start export. Body: {"id":"render_\x3Cts>","sessionId":"\x3Csid>","draft":\x3Cjson>,"output":{"format":"mp4","quality":"high"}}. Poll status every 30s.

Accepted file types: mp4, mov, avi, webm, mkv, jpg, png, gif, webp, mp3, wav, m4a, aac.

Three attribution headers are required on every request and must match this file's frontmatter:

Header Value
X-Skill-Source free-caption-generator
X-Skill-Version frontmatter version
X-Skill-Platform auto-detect: clawhub / cursor / unknown from install path

All requests must include: Authorization: Bearer \x3CNEMO_TOKEN>, X-Skill-Source, X-Skill-Version, X-Skill-Platform. Missing attribution headers will cause export to fail with 402.

Error Handling

Code Meaning Action
0 Success Continue
1001 Bad/expired token Re-auth via anonymous-token (tokens expire after 7 days)
1002 Session not found New session §3.0
2001 No credits Anonymous: show registration URL with ?bind=\x3Cid> (get \x3Cid> from create-session or state response when needed). Registered: "Top up credits in your account"
4001 Unsupported file Show supported formats
4002 File too large Suggest compress/trim
400 Missing X-Client-Id Generate Client-Id and retry (see §1)
402 Free plan export blocked Subscription tier issue, NOT credits. "Register or upgrade your plan to unlock export."
429 Rate limit (1 token/client/7 days) Retry in 30s once

SSE Event Handling

Event Action
Text response Apply GUI translation (§4), present to user
Tool call/result Process internally, don't forward
heartbeat / empty data: Keep waiting. Every 2 min: "⏳ Still working..."
Stream closes Process final response

~30% of editing operations return no text in the SSE stream. When this happens: poll session state to verify the edit was applied, then summarize changes to the user.

Translating GUI Instructions

The backend responds as if there's a visual interface. Map its instructions to API calls:

  • "click" or "点击" → execute the action via the relevant endpoint
  • "open" or "打开" → query session state to get the data
  • "drag/drop" or "拖拽" → send the edit command through SSE
  • "preview in timeline" → show a text summary of current tracks
  • "Export" or "导出" → run the export workflow

Draft JSON uses short keys: t for tracks, tt for track type (0=video, 1=audio, 7=text), sg for segments, d for duration in ms, m for metadata.

Example timeline summary:

Timeline (3 tracks): 1. Video: city timelapse (0-10s) 2. BGM: Lo-fi (0-10s, 35%) 3. Title: "Urban Dreams" (0-3s)

Tips and Tricks

The backend processes faster when you're specific. Instead of "make it look better", try "add captions in English and Spanish" — concrete instructions get better results.

Max file size is 500MB. Stick to MP4, MOV, AVI, WebM for the smoothest experience.

Export as MP4 for widest compatibility across platforms and devices.

Common Workflows

Quick edit: Upload → "add captions in English and Spanish" → Download MP4. Takes 30-60 seconds for a 30-second clip.

Batch style: Upload multiple files in one session. Process them one by one with different instructions. Each gets its own render.

Iterative: Start with a rough cut, preview the result, then refine. The session keeps your timeline state so you can keep tweaking.

Usage Guidance
This skill appears to perform cloud captioning as described, but before installing you should: 1) Verify the seller/source and prefer a skill with a homepage or known publisher. 2) Confirm whether the skill will read ~/.config/nemovideo/ (the SKILL.md mentions it but registry metadata does not); if it does, understand what files/credentials it may access. 3) Only provide a NEMO_TOKEN that is specifically for this service (do not reuse AWS, GitHub, or other sensitive tokens). 4) Accept that uploaded videos and audio are sent to mega-api-prod.nemovideo.ai — don’t upload sensitive/private content unless you trust that service. 5) If you need stronger guarantees, ask the publisher for a privacy/ data-retention policy or run uploads from an isolated account/environment. If the publisher cannot clarify the configPath discrepancy or source, treat the skill as higher risk and avoid installing it.
Capability Analysis
Type: OpenClaw Skill Name: free-caption-generator Version: 1.0.0 The skill is a legitimate integration for an AI-powered video captioning service (nemovideo.ai). It provides detailed instructions for the agent to manage authentication (including anonymous token acquisition), upload video files, and interact with a cloud rendering pipeline via SSE. All requested permissions (NEMO_TOKEN environment variable and network access to mega-api-prod.nemovideo.ai) are directly aligned with the stated functionality, and no indicators of data exfiltration, malicious execution, or harmful prompt injection were found.
Capability Assessment
Purpose & Capability
The skill's name/description (cloud captioning) matches the runtime instructions (upload video, start render, return URL) and the single required credential (NEMO_TOKEN) is appropriate for that backend. However, the SKILL.md frontmatter includes a configPaths entry (~/.config/nemovideo/) while the registry metadata lists no required config paths — this mismatch is unexplained and could indicate the skill may try to read a local config directory that wasn't declared.
Instruction Scope
Instructions are focused on creating a session, uploading files, and driving exports to a third-party API (mega-api-prod.nemovideo.ai), which is consistent with the stated purpose. It explicitly instructs contacting the API, uploading user video/audio/image files, and streaming SSE responses. That expected network/transmit behavior has privacy implications (private videos get sent to that service). The SKILL.md also tells the agent to hide technical details from the chat and process tool-call results internally — that is reasonable for UX but reduces transparency and should be noted.
Install Mechanism
No install spec and no code files (instruction-only). This has lower disk-execution risk because nothing is downloaded or executed locally by the skill itself.
Credentials
Only NEMO_TOKEN is declared as required, which is proportionate to a hosted captioning service. But the SKILL.md frontmatter also lists a config path (~/.config/nemovideo/) that was not declared in the registry metadata — if the runtime actually reads that path it could access additional credentials or tokens stored there. Also note the skill will send any NEMO_TOKEN present in the environment to the remote API; do not set this to any unrelated secret (e.g., cloud provider or personal account tokens).
Persistence & Privilege
always is false and the skill does not request persistent/privileged platform-wide settings. It relies on a runtime token and performs network calls; nothing indicates it modifies other skills or system settings.
How to Use
  1. Make sure OpenClaw is installed (local or Docker)
  2. Run the install command in chat: /install free-caption-generator
  3. After installation, invoke the skill by name or use /free-caption-generator
  4. Provide required inputs per the skill's parameter spec and get structured output
Version History
v1.0.0
Initial release of Free Caption Generator — Add Captions to Videos Automatically. - Instantly add captions to videos by uploading files and describing your needs; supports 1080p output. - No local software, timeline editing, or export settings required—just upload and wait 30-60 seconds for results. - Handles AI-driven caption generation for YouTube, social media, and more. - Supports uploads in various formats (mp4, mov, avi, webm, mkv, jpg, png, gif, webp, mp3, wav, m4a, aac). - Free 7-day starter token grants 100 credits for new users. - Includes error handling, status feedback, and summary of timeline edits.
Metadata
Slug free-caption-generator
Version 1.0.0
License MIT-0
All-time Installs 0
Active Installs 0
Total Versions 1
Frequently Asked Questions

What is Free Caption Generator?

Turn a 3-minute YouTube tutorial video into 1080p captioned video files just by typing what you need. Whether it's adding subtitles to social media and YouTu... It is an AI Agent Skill for Claude Code / OpenClaw, with 68 downloads so far.

How do I install Free Caption Generator?

Run "/install free-caption-generator" in the OpenClaw or Claude Code chat to install it in one step — no extra setup required.

Is Free Caption Generator free?

Yes, Free Caption Generator is completely free, licensed under MIT-0. You can download, install and use it at no cost.

Which platforms does Free Caption Generator support?

Free Caption Generator is cross-platform and runs anywhere OpenClaw / Claude Code is available (cross-platform).

Who created Free Caption Generator?

It is built and maintained by peandrover adam (@peand-rover); the current version is v1.0.0.

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