Social Post Studio

OverviewCopy Anchor Link

One call turns a topic into a post you can publish: an AI-generated image, a caption written for the platform, and a set of hashtags.

Endpoint: POST /v1/social/posts/generate

It composes the two metered surfaces it sits beside — image generation and the LLM — and bills as exactly that: the caption at the drafting model's token rate, the image at your chosen model's per-image rate. Both figures come back on every response.

1. 1

   Your app

   Send a (and optionally a , and )

2. 2

   CallMissed gateway

   Draft the caption and hashtags, then render the image

3. 3

   Image model

   Produce the post image

4. 4

   Your app

   Publish the caption, hashtags and image

Basic UsageCopy Anchor Link

import requests

res = requests.post(
    "https://api.callmissed.com/v1/social/posts/generate",
    headers={"Authorization": "Bearer cm_your_key"},
    json={
        "topic": "our bakery's new sourdough, baked fresh at 6am",
        "platform": "instagram",
        "tone": "warm",
        "hashtag_count": 8,
        "image_model": "flux-2-klein-9b",
        "size": "1024x1024",
    },
).json()

print(res["caption"])
print(" ".join(res["hashtags"]))
# res["image"]["b64_json"] → base64 PNG
# res["credits"]["total"]  → what this post cost

ParametersCopy Anchor Link

Caption length follows the platform: 2,200 characters for instagram, 5,000 for facebook. generic uses the smaller of the two, so one draft is publishable on either.

Reference images and a brand PDFCopy Anchor Link

Pass reference_images to put your real brand assets in the generated picture — a logo, a product shot, a packaging photo. The image is then produced as an edit of those references rather than a text-only generation, so the mark in the output is yours instead of an invented lookalike.

Each item is base64, either bare or as a full data:image/png;base64,… URL (what a browser's FileReader.readAsDataURL gives you, so no string surgery needed). PNG and JPEG only — the format is checked from the file's own bytes, not from a declared type. Up to 16 images, each at most 10 MB decoded (nano-banana-2, nano-banana-pro and gemini-3.1-flash-lite-image: up to 14 images, each at most 7 MB, 14 MB in total).

reference_pdf is a different kind of reference: a brand guideline, a spec sheet or a menu, whose text is extracted and folded into the image prompt as context. The file itself never reaches the image model, and a PDF with no extractable text (a scan) is ignored rather than failing the call. At most 10 MB decoded. Because only text reaches the model, it works with any image_model.

Reference images require an image model with an edit surface: gpt-image-2.5-sunburst, gpt-image-2.5-flare, gpt-image-2, gpt-image-1.5, nano-banana-2, nano-banana-pro or gemini-3.1-flash-lite-image. Sent with any other image_model, the request fails 422 before a single credit is reserved. That is deliberate — the alternative is quietly dropping your references and charging full price for a picture carrying none of your branding. For the same reason, a reference-carrying request will not silently fall back to a model that cannot honour them.

Pricing does not change on the gpt-image-* models. A referenced image is billed at exactly the same per-image rate as a plain generation of the same model, size and quality. nano-banana-2, nano-banana-pro and gemini-3.1-flash-lite-image add a small per-reference charge — see image pricing.

curl -X POST https://api.callmissed.com/v1/social/posts/generate \
  -H "Authorization: Bearer cm_your_key" \
  -H "Content-Type: application/json" \
  -d '{
    "topic": "our winter service package, booked till February",
    "platform": "instagram",
    "image_model": "gpt-image-2.5-sunburst",
    "reference_images": ["data:image/png;base64,iVBORw0KGgoAAAANS..."],
    "reference_pdf": "JVBERi0xLjQKJcfs..."
  }'

How the image prompt is writtenCopy Anchor Link

When you don't pass image_prompt, the endpoint does not send your topic to the image model directly. A marketing topic ("winter tune-up, ₹1,200, booked until February") sent to an image model renders the words literally — garbled numbers, invented signage. Instead the caption drafter produces a separate, purely-visual prompt: it keeps the facts (prices, dates, your business name) in the caption, and describes a real, photographable scene for the image. The result is a photo that represents the offer rather than a picture trying to spell it out.

Pass your own image_prompt to override this and control the image directly.

ResponseCopy Anchor Link

{
  "created": 1731234567,
  "topic": "our bakery's new sourdough, baked fresh at 6am",
  "platform": "instagram",
  "caption": "Pulled from the oven at 6am. Crackling crust, open crumb, still warm.",
  "hashtags": ["#sourdough", "#freshbread", "#bakery"],
  "image": {
    "b64_json": "<base64 PNG>",
    "revised_prompt": null,
    "url": "https://...signed-url..."
  },
  "model_used": "glm-4.7-flash",
  "image_model_used": "flux-2-klein-9b",
  "credits": {
    "image": 10.0,
    "llm": 0.065,
    "total": 10.065
  }
}

image.url is a short-lived signed link — download or re-host it promptly. The base64 payload in the same response has no expiry.

Generated images also appear in GET /v1/images/history alongside your other generations.

PermissionsCopy Anchor Link

A key missing the permission for a leg gets 403 permission_denied before anything is generated or charged.

PricingCopy Anchor Link

Billed as two separate line items on your usage, at the same rates as calling the endpoints individually:

• Caption + hashtags — per token, at the drafting model's rate. A typical post is well under one credit.
• Image — the flat per-image price of image_model, plus any per-reference charge. See the image pricing table.

Every response carries the exact split in credits. A caption-only call is charged for the caption alone.

Image credits are reserved before generation and refunded in full if the post does not complete — and a request that fails is never charged for the caption either. A failed post costs nothing.

ErrorsCopy Anchor Link