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Edit video and audio with local FFmpeg from natural-language requests: cut, trim, join, resize/reframe (9:16, 1:1), speed change, captions and subtitles (SRT/ASS, animated, karaoke), logos and text overlays, lower-thirds and titles, silence removal, multicam and external-mic sync, loudness normalisation, HDR/Dolby Vision to SDR, LUTs, background music with ducking, platform exports (YouTube, Reels, TikTok, X), compliance checks, scene detection and highlight reels, contact sheets to inspect results, and whole-edit project files. Use this skill whenever the user mentions a video or audio file (mp4, mov, mkv, wav, m4a), footage, a clip, captions, subtitles, a reel or short, YouTube/Instagram/TikTok delivery, LUFS, sync, transcoding, ffmpeg, or asks to make something "60 seconds", "vertical", "louder", "captioned" — even when they do not say "edit". Python 3.10+ standard library only (3.9 deprecated), no cloud, no API keys.

kajisho5/ffmpeg-skill Agent Skills author: kajisho5 MIT 80 files · 11 scripts body ≈ 7 170 tokens Open the sourcegithub.com↗ analyzed 3 d ago

Edit video and audio with local FFmpeg from natural-language requests: cut, trim, join, resize/reframe (9:16, 1:1), speed change, captions and subtitles…

As a process C 52/100 · Has gaps — References files that are not bundled: references/gotchas.md, references/gotchas.md, references/gotchas.md

GeneratorYouTubeMedia and videoMarketingtype and topics are labelled automatically from the skill text
Runs in: Claude / Claude Code ChatGPT / Codex Gemini CLI Cursor GitHub Copilot / VS Code Qwen Code Kimi Code CLI Z.ai (GLM) DeepSeek (Deep Code) Mistral Vibe LangChain (deepagents) OpenClaw Goose OpenCode
JSON
Technical rating
C
84/100
safety, quality, tests
Safety 60%
100
Quality 40%
60
Run on models
none yet
Process rating
C
52/100
Has gaps
References files that are not bundled: references/gotchas.md, references/gotchas.md, references/gotchas.md
Tools and files w 18
0
Result and completion w 14
0
Inputs and preconditions w 11
0
the three weakest of ten parameters · all ten

How to improve

  1. The SKILL.md body is over 5,000 tokens: move reference detail into references/ and load it when needed.
  2. The text references files that are not there: add them or drop the references.
For the model run — optional
  • Your own cases (evals/evals.json, 4–6 real requests with expected answers): the full check would then run those instead of a model-drafted suite.
  • A spec.yaml with trigger phrases and assertions — a behaviour contract for CI; `skilltest init` writes a template.

Guard findings · 0

✓ No critical or high findings

Files scanned: 34. Evidence is masked. Grey chips explain why severity was lowered.

Against the Agent Skills spec

  • warning body-long SKILL.md body ≈ 7170 tokens (recommended < 5000); move details to references/
  • warning missing-ref reference to a missing file: references/gotchas.md
  • warning missing-ref reference to a missing file: references/gotchas.md
  • warning missing-ref reference to a missing file: references/gotchas.md
  • warning missing-ref reference to a missing file: references/gotchas.md
  • warning missing-ref reference to a missing file: references/gotchas.md
  • warning missing-ref reference to a missing file: references/gotchas.md
  • warning missing-ref reference to a missing file: references/gotchas.md
  • warning missing-ref reference to a missing file: references/gotchas.md
  • warning missing-ref reference to a missing file: references/gotchas.md
  • warning missing-ref reference to a missing file: references/gotchas.md
  • warning missing-ref reference to a missing file: references/gotchas.md
  • warning missing-ref reference to a missing file: references/gotchas.md
  • warning missing-ref reference to a missing file: references/gotchas.md
  • warning missing-ref reference to a missing file: references/scripts.md
  • warning missing-ref reference to a missing file: references/devices.md
  • warning missing-ref reference to a missing file: references/gotchas.md
  • warning missing-ref reference to a missing file: scripts/*.py
  • warning missing-ref reference to a missing file: references/gotchas.md

Process rating: all ten parameters 52/100

Will not run. References files that are not bundled: references/gotchas.md, references/gotchas.md, references/gotchas.md
  • 0Tools and files. 18 referenced file(s) missing: references/gotchas.md, references/gotchas.md, references/gotchas.md
  • 0Result and completion. Does not say what the result is
  • 0Inputs and preconditions. Does not say what the process needs to start
  • 30Running it twice. 14 mutating operations with no state check
  • 70Execution cost. Instruction body is 7170 tokens
  • 100Steps. 38 steps
  • 100When it triggers. States when to use and when not to
  • 100Failures and branches. 3 branches, has a failure section
  • 100Consistency. Name and required fields are in place
  • 100Progress reporting. Reports progress
  • medium Safety rules and hard prohibitions inside a skill: they belong in the system prompt, here they protect nothing
  • low The response is described with custom markup (4 tags): a typed call is more reliable

Everything here is measured from the skill text rather than judged by a model, so the numbers are checkable. A parameter weighs more when it is a more common reason for the process to stall.

Quality signals

  • +4Description does not say when NOT to use the skill (false activations)
  • +3Description length 934: 120–800 characters recommended
  • +3Output format is not stated: the model decides each time
  • -44 reference files, but SKILL.md never points to them: the model will not open them
  • +1No license
  • +2Single-language instructions
  • +5Description quotes 4 example trigger phrases
  • +4Structure: 8 headings
  • +3Step-by-step instructions: 38 items
  • +4Has examples (3 code blocks)

Quality base 70; lint remarks subtract, signals add up to 100. Result: 60.