This is an example of an agent you can build in Sylvie: hand it the edit, the on-screen hook or just the idea, and it writes the TikTok caption, the few words that have to land before the truncation, the search terms people actually type, a prompt that opens the comment section, and the hashtags and disclosure your brand uses. It runs on your brand brain (how each account talks, what the community responds to, live offers and product facts, the claims and phrases you avoid, the videos that already worked), so it reads native instead of like a brand doing an impression of the platform. Sylvie does not ship this agent pre-built: you assemble it and point it at your own accounts.
Sylvie does not ship this agent pre-built. It is an example of an agent your team can build with Sylvie, powered by your brand brain, so it runs your workflow the way you actually run it.
The TikTok Caption agent is an example of what a social team can build on top of its brand brain in Sylvie. Give it the video, or just the concept behind it, and it returns the caption in full: a first line short enough to survive TikTok's truncation, the keywords that make the video findable in search, the question or provocation that gets the comments going, the hashtag set the account uses, and any paid partnership or regulated wording the post has to carry.
On TikTok the caption is small and does a surprising amount of work. It is the search index for a video that will keep getting served for months, it is where the comment section gets opened, and it is the fastest place for a brand to sound like a tourist. Post four or five times a week across several accounts and all three problems compound, so an agent built on your brand brain keeps voice, keywords and compliance consistent whoever briefs the post.
Before it writes, the agent reads that account's brain: the register the community expects, the running jokes and references the account has earned the right to use, the product facts, prices and live offers it may state, the claims and phrases the brand never touches, the disclosure rules for paid and creator content, and the captions on the videos that already performed. It knows which offer is current, and it will not invent a spec or a discount.
Then it drafts inside Sylvie, shaped for TikTok specifically: a truncation-proof opening, search terms placed naturally rather than stuffed, a length that fits the format (a talking-head clip, a photo carousel, part four of a series), and the CTA that matches the goal, whether that is a comment, a follow, a stitch or a link in bio. It returns several options with hook variants, flags anything it cannot support, and every caption stays sourced back to the brain it came from.
TikTok cuts the caption off almost immediately, so the agent writes an opening built to work in a handful of words and earn the tap for more.
It places the terms your audience actually types into the search bar, so a video keeps pulling views long after it has finished its run on the For You page.
The register each account has earned lives in its brain, so a dermatology brand and a hot sauce brand never end up with the same caption energy, whoever is briefing that day.
Each caption ends on the question, the duet invitation or the mild provocation that gets the comment section moving, because that is the signal the platform compounds.
Paid partnership wording, #ad, regulated category rules and the words your brand cannot say are rules in the brain, not something a junior has to remember at six on a Friday.
Point it at the whole batch of edits and it captions them in your voice, so the calendar stays full through a shoot week or across a full client roster.
TikTok rewards volume and native tone, which is exactly where in-house teams and agencies run out of hours. These are moments where teams point this agent at their brand brain and caption at the pace the platform demands.
The shoot is done, the editor has delivered, and nothing can be scheduled until every video has a caption. The agent writes all twenty from the brand brain, each with its own hook and search terms. The batch is queued the same afternoon instead of trickling out over two weeks while the content ages.
A trend fits the brand and the window closes tonight. The agent drafts the caption in the account's voice with a comment prompt tuned to the joke, so the post ships while the sound is still climbing. You arrive early instead of three days late, when a trend post reads as a brand catching up.
Your weekly explainer series deserves more than a week of life. The agent captions each episode with the phrases people search, plus the part number and the pull back to episode one. Later episodes start outperforming their launch week because search keeps delivering new viewers months on.
Five creators deliver videos for a campaign and each caption has to sound like them, state the offer correctly and carry the disclosure. The agent drafts a caption per creator from the brief in the brain. The campaign goes live on time with wording legal has signed off and nothing to take down later.
A launch lands and every brand on your roster needs its own version, at its own price, in its own tone. The agent captions each from that brand's isolated brain. The whole roster posts on launch morning with the right facts and no cross-contamination between accounts.
One comment on last week's video is asking the question your whole audience has. The agent writes the caption for the reply video, carrying the original question into the search terms and setting up the next one. A single comment becomes a post that outperforms the video it came from.
It reads like a brand when it is guessing. This agent is not guessing: it writes from your account's brain, the register you have earned, the phrases your community uses, the jokes that landed, the things you never say. That is the whole difference between native and try-hard, and it comes from your material rather than from a prompt asking for a casual tone.
It is the smallest part and one of the hardest working. It is how the video gets found in TikTok search weeks later, it is where the comment section gets opened, and it is where a loose claim or a missing disclosure becomes a real problem. The video earns the watch, the caption decides how long it keeps earning.
You decide that when you build it. Many teams build this one narrowly for captions and chain it to a separate hook or video script agent on the same brand brain, so the on-screen text, the spoken hook and the caption all agree. Because you assemble the workflow yourself, you scope it to how your team really produces video.
You build it, on your own brand, inside Sylvie. You connect the account, approve what the agent may read from the brain and describe how you caption, and Sylvie assembles the workflow around that, usually within an afternoon. The agent on this page is an example of what teams build for themselves, not a product you switch on.
It carries the rules as well as the voice: the claims your category cannot make, the substantiation each claim needs, the disclosure language for paid and creator posts, and which offers are currently live. The agent drafts against that and flags anything it cannot support, and a human still approves before anything publishes.
Yes. Every brand has its own permission-aware, isolated brain, so one client's tone, offers or product facts are never reachable from another client's captions. You build a version per account, each one sharpens as its brain fills up, and nothing you put in trains a foundation model.
Book a demo and we will map the workflows worth turning into agents, and show how each one runs on your brand brain.
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