How to Write Your YouTube Title, Chapters and Tags

Choose Workflow → Prepare for YouTube…, pick your exported video, click Transcribe, then Write with the SEO Agent. You get five titles, a description, chapters and tags drafted from the transcript and a short brief you fill in — then you edit them, upload the video yourself in YouTube Studio, and apply the finished words to it from MediaFlowSwift.

That’s the shape of it. The rest of this page is each step, what gets checked before anything can go live, and what’s sent where while you’re writing.

What Prepare for YouTube works on

Prepare for YouTube works on the finished video you exported from your editor, not on the project’s clips. MediaFlow reads the file, transcribes what is said in it, and an SEO agent writes the words that go with it. You edit them.

1. Choose Workflow → Prepare for YouTube…
2. Click Choose Video… and pick the exported video — it’s only read, never changed or sent anywhere
3. Click Transcribe. A long video takes a few minutes
4. Fill in Your brief: who the video is for, the tone you want, and anything the description must include — one item per line, such as links, credits or a call to action
5. Click Write with the SEO Agent
6. Edit anything you like. Click one of the other four titles to use it instead
7. Upload the video in YouTube Studio, then apply what you wrote to it

What the agent actually does

Reads the transcript and works out what the video is, who it is for, and the main phrase: the few words someone would most likely type to find it

From there:

Writes a first draft: five titles that take different approaches, a description, chapters at the points where the subject changes, tags, and three suggestions for the words on the thumbnail

Then it checks its own work and revises:

Checks the draft against the checklist, is given every fault it found, re-reads the draft as a viewer would, and revises. It always revises once, and again if something that must be fixed remains

A revision that makes the draft worse is never used, and anything still wrong when it’s done shows up in the checklist for you to fix yourself — you have the last word, not the agent.

Where the transcript goes while it’s writing

Writing the draft is off until you turn it on, and what gets sent depends on which model you’ve chosen in Settings › Analysis:

This is off until you turn it on. In Settings › Privacy, switch on “A model that writes your YouTube title, description and tags”. While it is off and a paid provider is chosen, Write with the SEO Agent tells you where the switch is and sends nothing.

With the model that runs on this Mac, the transcript never leaves it — unless you’ve pointed that local model at another computer on your network, in which case the transcript, the video’s length and your brief go only as far as that computer. Pick a paid provider (Claude, ChatGPT or Gemini, with your own API key) instead, and the transcript, the video’s length, your brief, and then the agent’s own drafts for revision go to that provider — never the video itself, or its file name.

What has to be true before YouTube will show it

The checklist beside the editor runs on whatever’s in the fields, whether you wrote it or the agent did. The red items, things YouTube enforces or that break a feature:

• Title — not empty, and no more than 100 characters
• Description — not empty, and no more than 5,000 characters, chapters included
• The characters < and > — YouTube does not accept them in a title or a description
• Your brief — every line under Must include appears in the description, word for word
• Chapters — the first starts at 0:00, there are at least three, none is shorter than 10 seconds, and none starts after the video ends. If any of these fails, YouTube shows no chapters at all
• Tags — no more than 500 characters in total, counted the way YouTube counts: commas included, and two extra for each tag that contains a space

Past that, the rest is advice, not a YouTube rule: a title cut off in search past about 60 characters, your main phrase placed early in the title and within the first 150 characters of the description, capitals that make a title harder to scan, and tags that aren’t repeated.

Getting the words onto the video

The public video is always uploaded by you, in YouTube Studio — not by MediaFlowSwift:

That is how the video goes public: uploaded by you, in YouTube Studio, with no Google Cloud audit standing between you and the visibility you choose there.

Once it’s up, Apply to the Video I Uploaded… finds it on your channel (you confirm which one), and sets the title, description with chapters at its end, and tags on it — reading the video first so nothing else on it changes. Copy Title, Copy Description and Copy Tags are there too, if you’d rather paste the words in by hand. Applying is off until you turn on Sending to YouTube in Settings › Privacy. It also needs a Google client of your own, which takes about ten minutes to set up once.

Read what it wrote before it goes out

Read what it writes before you publish it. The agent works from a transcript, and speech recognition mishears names, places and technical words. A wrong name in a title is your name on a mistake.

Read more

• Preparing a Video for YouTube — the full workflow, step by step
• The SEO Agent — what it does, which model writes it, and what’s sent where
• The Publishing Checklist — every check, red and grey, in full
• Applying Your Details to the Video You Uploaded — what Apply changes on the video, and what it never touches

Other guides

• How to Find a Clip by What Was Said in It on a Mac — the same on-this-Mac transcription that feeds this draft.

All guides — the full list.

Try it on your own footage

MediaFlowSwift is the Mac app this guide describes. Download it and the full app runs for 14 days, with no card asked for — macOS 14 or later, on a Mac with Apple silicon.