How to write social media captions with AI

AI can write a social media caption in seconds. Whether that caption is any good depends almost entirely on what you tell it. Ask for "a caption for our new latte" and you get something generic. Give it the brand's voice, the audience, the offer and the network, and you get a draft worth editing.

This guide shows what context to give an AI writing tool, a brief you can copy, how to adapt captions for each network, and what to check before anything is posted.

What AI does well, and what it does not

Good at:

• First drafts, quickly, in several versions.
• Shortening, lengthening and changing the tone of a text.
• Rewriting one idea for different networks.
• Suggesting hashtags and calls to action.

Not good at, without your help:

• Knowing facts it was not given: your prices, opening hours, dates and names.
• Sounding like your brand, unless you describe the voice.
• Knowing what is true about your product. It can write confident sentences that are wrong.

So treat AI as a fast first writer and yourself as the editor.

Give the AI a brand voice

Before you ask for any caption, write a short description of the brand that you reuse every time:

• Voice: three or four words, such as warm, direct, a little playful.
• Audience: who you are talking to, and what they care about.
• Words to use and avoid: phrases the brand always says, and ones it never does.
• Hashtags: the brand's own tags and a few topic tags.
• Language: the language the posts are written in.

In KariSMMa, this lives in the brand kit, and the AI assistant reads it for every caption. When you add a brand, KariSMMa fills in the kit from the website or the brand's social profiles, and you adjust it.

A caption brief you can copy

Give the AI these details for each post. The more specific, the better the draft:

• Goal: what you want people to do, such as visit, book, reply or save.
• Topic: what the post is about, in one sentence.
• Facts: prices, dates, times and names, written exactly.
• Network and format: for example, an Instagram Reel or a Facebook post.
• Length: one line, a short paragraph, or a longer story.
• Call to action: the last line, such as "Book through the link in our profile".

For example, for a fictional coffee shop:

Goal: get people to try the new drink this week. Topic: our oat milk pumpkin latte is back from Monday. Facts: available Monday to Sunday, 7 am to 6 pm, at both shops. Network: Instagram post with a photo. Length: two short lines. Call to action: come in this week. Voice: warm and simple, no exclamation marks.

Tailor the caption for each network

The same idea needs a different caption on each network:

• Instagram: the first line matters most, because the rest is cut off in the feed. Up to 2,200 characters and up to 30 hashtags are allowed, but a few relevant tags work better.
• Facebook: longer captions and links work well, and hashtags matter less.
• Threads: short and conversational; a post is limited to 500 characters.
• TikTok and YouTube Shorts: the caption supports the video; keep it short and searchable.

KariSMMa's Tailor per network takes one caption and rewrites a version for every selected network, keeping each one editable, with a character counter for each network's limit. Read more about creating and scheduling posts.

Edit before you post

Read every AI caption before it is published. Check:

1. Facts: prices, dates, times, names and links.
2. Claims: nothing the business cannot back up, especially for health, finance and legal topics.
3. Voice: it sounds like the brand, not like a template.
4. Clichés: remove filler phrases that could fit any brand.
5. Accessibility: plain words, and alt text for images.
6. The network's rules: length, hashtags, and no links where they will not work.

If someone else should approve the post, send it for approval before it is scheduled.

Captions for different goals

Change the brief when the goal changes:

• Awareness: lead with something surprising or useful, and keep it short.
• Engagement: end with a simple question people can answer in a few words.
• Sales: put the offer, the price and the deadline in the first two lines.
• Bookings: say exactly how to book, and repeat the key detail, such as the date.
• Community: thank people by name (with their permission) and share their photos or reviews.

Mistakes to avoid

• Publishing the first draft. It is rarely the best one. Edit it, or ask for another angle.
• Letting the AI invent details. If a fact is not in your brief, it should not be in the caption.
• The same caption everywhere. Each network has its own length and habits.
• Too many hashtags. A few relevant ones help people find the post; a wall of them looks like spam.

Ask for options, then combine

Ask for three versions with different angles: one practical, one emotional, one with a question. Pick the best line from each. You will write faster than starting from a blank page, and the result will sound more like you.

How this works in KariSMMa

In Create post, Draft with AI writes a whole post from a few words, captions are written for every selected network in the brand's voice, and hashtags are suggested per network. Each action spends a few points from your plan, for example 3 points for a caption set, or none if you connect your own AI key. Nothing is posted until you schedule it. When you want the AI to plan a whole week, Autopilot drafts the posts and, in Semi-auto, waits for your approval.