Which sizes does the social-square template support?

1080×1080, 1080×1350. The default is 1080×1080; pass width and height to pick another supported size.

Which parameters are required?

headline. Every other parameter is optional and has a rendering default.

Does rendering the same parameters twice cost twice?

No. The same template version, parameters, brand kit version, format, and size produce the same cache key, so a repeat request is served from cache instead of rendering again. Billing is not connected yet in early access.

Template · social-square@1

Social square template

The social-square template renders a square or 4:5 feed post with a large headline, short body, handle, and call to action. Send JSON parameters through the remote MCP server, POST /v1/renders, or a signed /i/social-square.png URL; the default size is 1080×1080.

Sizes: 1080×1080 · 1080×1350
Formats: PNG · JPEG · WebP
Version: 1.0.0

VectorFast Render is in early access. Billing is not connected yet, and API keys are issued to waitlist members as access opens. Join the waitlist

Preview

Rendered by VectorFast Render from this template's English and Chinese example parameters, through the same signed URLs your own pages would use.

Preview images are signed on the server and are not available in this environment.

Ask your agent

Paste the prompt into Claude, Cursor, or another agent connected to the VectorFast Render MCP server. The JSON is the render tool call it should turn into.

Prompt

Make a 4:5 Instagram portrait post announcing that agents can now ship on-brand images, signed @vectorfast, with a "Join the waitlist" button.

MCP render call

{
  "name": "render",
  "arguments": {
    "template": "social-square",
    "params": {
      "headline": "Your agent now ships on-brand images",
      "body": "Connect once, pick a template, pass the copy.",
      "handle": "@vectorfast",
      "cta": "Join the waitlist"
    },
    "width": 1080,
    "height": 1350
  }
}

Connect Claude to VectorFast Render

Parameters

Read from the schema that POST /v1/renders validates. String values are trimmed; anything over a limit is rejected with invalid_params.

Social square template parameters
Param	Type	Required	Limit	Notes
headline	string	Yes	≤ 90 chars	Large headline.
body	string	No	≤ 160 chars	Short supporting copy.
handle	string	No	≤ 40 chars	Account handle such as "@vectorfast".
cta	string	No	≤ 30 chars	Button text.

Render it from code

The REST call needs an API key in Authorization: Bearer. Its response includes a signed url you can store and reuse as an og:image. The Node.js function shows the signing algorithm the server verifies; per-key signing secrets are not issued yet in early access, and the secret must stay on your server.

curl · POST /v1/renders

curl https://vectorfast.ai/v1/renders \
  -H "Authorization: Bearer $VECTORFAST_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
  "template": "social-square@1",
  "format": "png",
  "width": 1080,
  "height": 1350,
  "params": {
    "headline": "Your agent now ships on-brand images",
    "body": "Connect once, pick a template, pass the copy.",
    "handle": "@vectorfast",
    "cta": "Join the waitlist"
  }
}'

Node.js · signed URL (server-side only)

import { createHmac } from 'node:crypto'

// Server-side only. Never ship the signing secret to a browser, a mobile app or a repo.
const SIGNING_SECRET = process.env.VECTORFAST_SIGNING_SECRET

function encode(value) {
  return encodeURIComponent(value).replace(/[!'()*]/g, c => '%' + c.charCodeAt(0).toString(16).toUpperCase())
}

export function signRenderUrl({ template, format = 'png', params, brand, width, height, keyId }, secret = SIGNING_SECRET) {
  const query = {}
  for (const [key, value] of Object.entries(params)) {
    if (value === undefined || value === null)
      continue
    query[key] = typeof value === 'string' ? value : Array.isArray(value) ? JSON.stringify(value) : String(value)
  }
  if (brand) query.brand = brand
  if (keyId) query.k = keyId
  if (width) query.w = String(width)
  if (height) query.h = String(height)

  const canonical = Object.entries(query)
    .map(([key, value]) => [encode(key), encode(value)])
    .sort((a, b) => (a[0] < b[0] ? -1 : a[0] > b[0] ? 1 : a[1] < b[1] ? -1 : a[1] > b[1] ? 1 : 0))
    .map(([key, value]) => key + '=' + value)
    .join('&')
  const path = '/i/' + template + '.' + format
  const sig = createHmac('sha256', secret).update(path + '?' + canonical).digest('base64url')
  return 'https://vectorfast.ai' + path + '?' + (canonical ? canonical + '&' : '') + 'sig=' + sig
}

const url = signRenderUrl({
  template: 'social-square',
  format: 'png',
  width: 1080,
  height: 1350,
  params: {
    "headline": "Your agent now ships on-brand images",
    "body": "Connect once, pick a template, pass the copy. Every render matches the brand kit.",
    "handle": "@vectorfast",
    "cta": "Join the waitlist"
  },
})

How signed URLs work

Social square template FAQ

Which sizes does the social-square template support?: 1080×1080, 1080×1350. The default is 1080×1080; pass width and height to pick another supported size.
Which parameters are required?: headline. Every other parameter is optional and has a rendering default.
Does rendering the same parameters twice cost twice?: No. The same template version, parameters, brand kit version, format, and size produce the same cache key, so a repeat request is served from cache instead of rendering again. Billing is not connected yet in early access.

Updated 2026-10-30 · Markdown version