AI for Social Media Posts: Captions, Visuals and a Content Calendar

AI can draft a week of captions, a content plan and the images for each post in a single sitting. The drafts only sound like you if you start with a brief: who you are, who reads you, and which posts you already like. Without one, you get the same upbeat filler as every other account.

This article covers a reusable brief, a path from one idea to seven posts, caption rules for Instagram, a calendar prompt, and which text and image models to run for each job. You can do all of it in a social media post generator or in any chat with a text model.

What an AI post generator does, and what stays your job

A text model turns a brief and an idea into drafts: captions, hooks, hashtag sets and a content table. An image model turns a description or your own photo into a visual.

Everything around that stays with you:

• Strategy. You decide what the account is for and which topics it covers. A model will happily invent content pillars, but it doesn't know your sales calendar.
• Facts. Prices, opening hours, product specs and quotes. Models fill gaps with numbers that sound right.
• Publishing and scheduling. These happen in the platform or your scheduling tool, not in the model.

Brief the model first

Write the brief once, save it in a notes file and paste it at the top of every request. It cuts most of the "sounds like AI" problem before it starts.

ROLE: You write social posts for [brand], a [what it is] in [place].
AUDIENCE: [one line: who they are, what they care about].
VOICE: [3 adjectives]. Short sentences. No exclamation marks.
NEVER USE: elevate, unlock, journey, "in today's world", emojis.
SAMPLES I LIKE:
1. [paste a real post]
2. [paste a real post]
3. [paste a real post]
FORMAT: [platform], under [N] words, plain text.
Copy

Here are the first two lines filled in for a coffee shop: "You write social posts for Grindhouse, a 20-seat coffee shop in Leeds. Audience: remote workers and students nearby who come for the wifi and stay for the pastries." Three real sample posts do more for tone than any list of adjectives.

Step by step: one idea into a week of posts

1. Brief. Paste the block above.
2. Angles. "Here is the idea: [oat-milk latte launch]. Give me 7 different angles: behind the scenes, customer story, how-to, myth and so on. One line each."
3. Drafts per platform. Pick 3-4 angles. "Write each as an Instagram caption and as a LinkedIn post, with a different length and structure for each platform."
4. Shorten. "Cut each draft by a third without losing the specific details."
5. Hooks. "Give me 5 alternative first lines for post 2. No questions, no 'did you know'."
6. Final edit. Read each draft, fix the facts and rewrite anything that still sounds generic.

People usually stumble at step 3 by asking for "a post for all platforms". The result is one medium-length text that fits none of them.

AI for Instagram captions

Only the first line or two show before "more", so the hook carries the caption. Ask for the hook explicitly and read it on its own. If that line wouldn't make you tap, rewrite it.

Put these in the request:

• Length. 50-150 words works for most brand posts. Give the model a hard limit.
• Line breaks. One idea per short paragraph, with blank lines between them.
• CTA. One action: a question, "save this" or "link in bio". Not three.
• Hashtags. 3-5 specific ones at the end. Tell the model to skip generic tags.
• Variants. Ask for three, each with a different kind of hook.

[brief]
Write 3 Instagram captions about [topic]. Under 120 words each.
Hook types: 1) a specific detail, 2) a bold claim, 3) a question.
One CTA each. 5 niche hashtags. No emojis.
Copy

To see it work, run a ready-made coffee-shop prompt and compare the three variants.

Building a content calendar with AI

Ask for a table, not prose. You can scan a table quickly and change it row by row in follow-up messages.

[brief]
Plan a 2-week Instagram content calendar starting [date].
Pillars: product, behind the scenes, community, tips.
Return a table: date | platform | pillar | format | hook | visual idea.
No more than 2 posts in a row from the same pillar.
Copy

Then refine it: "Move the product posts closer to the 15th, we launch then" or "Replace the two reels in week 2 with carousels." Three or four follow-ups usually make the table usable.

Treat the result as a planning draft. Copy the table into your spreadsheet or scheduler and check the dates against your own launches and holidays.

Which text model for which job

These are the costs per run in Moleculs as of October 2026. Current numbers are in the model catalogue, with the cost per run for each model.

Generate angles and the calendar on a 1-2 credit model. Then run the 3-4 posts you'll actually publish through Sonnet or Opus with the same brief. A failed cheap run costs one or two credits, while a failed Opus run costs 20, so test new prompts on a cheap model first. For trend research, open the sources Sonar Deep Research cites. A trend from last year makes a dated post.

Visuals for the post

Pick the image model for the task. Costs per run as of October 2026:

• GPT Image 2.5 Flare, 6 credits. Quick drafts to test a composition before you spend more.
• Nano Banana Editor, 8 credits. Edits your own photo: change the background or adjust the scene.
• Seedream v4.5, 13 credits. Photorealistic product and lifestyle shots.
• Ideogram v3, 14 credits. Posters and images with text on them.
• Nano Banana 2, 21 credits. Text rendering and edits that combine several images.
• Midjourney, 23 credits. An artistic style for mood posts.

Write the image prompt from the "visual idea" column of your calendar and add the format: "square 1:1" for the feed or "vertical 9:16" for stories. When you generate an image for the post, start with a draft on Flare and switch to a more expensive model once the composition works.

Editing before you publish

Run this checklist on every post:

• Facts. Check every number, price, date and claim against your own source. Delete anything you can't confirm.
• Clichés. Search for the words on your "never use" list, because models slip them back in.
• Read it aloud. If you wouldn't say it at the counter, rewrite it.
• Images. Zoom in on hands, labels and any text. Make sure the product in the image looks like your real product.
• Platform rules. Meta, TikTok and other platforms have rules on labelling AI-generated or AI-edited content. Check the current policy for each platform you post to.

Common mistakes

• No brief. The model falls back to a generic marketing voice. Paste the brief every time.
• One prompt for every platform. Instagram, LinkedIn and X need different lengths and structures, so ask for each separately.
• 30 hashtags. A wall of broad tags looks like spam. Use a few specific ones.
• Publishing the first draft. Ask for three variants and edit the best one by hand.
• Unreadable text on images. General image models often garble lettering. Use Ideogram v3 or Nano Banana 2 for text, or add it yourself in an editor.

If several people run the brand's accounts, keep one shared brief so everyone's drafts start from the same voice. For team setups, see AI for business teams.