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Introduction

PromptVEX is an AI video prompt testing platform. It helps you score, preview, and route prompts to the right video model — so you stop burning credits on bad ideas.

v0.4.2StableUpdated Apr 24, 2026

The PromptVEX loop

Every prompt goes through three stages, each scoped to cost. The expensive call is always last.

1Free · ~2s

Analyze

Claude scores motion, style, subject, lighting.

21–2 cr · ~30s

Preview

Keyframes or 5s 480p draft via fal.ai.

320 cr · 2–4 min

Render

Routed to Kling, Runway, or Veo.

Quickstart

Authenticate with your API key, then send a prompt to /v1/analyze. The response includes a score, four metrics, and three rewrites.

bash

curl https://api.promptvex.com/v1/analyze \
  -H "Authorization: Bearer $PROMPTVEX_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "prompt": "Slow dolly-in on a chrome teapot, morning light, 35mm.",
    "duration": 5,
    "aspect": "16:9"
  }'

A typical response looks like this:

json

{
  "score": 84,
  "metrics": {
    "motion_clarity": 92,
    "style_specificity": 78,
    "subject_ambiguity": 64,
    "lighting": 80
  },
  "recommended_model": "kling-1.6-pro",
  "rewrites": [
    "Slow 4s dolly-in on a polished chrome teapot ...",
    "Cinematic dolly-in, marble counter, morning sun ...",
    "Photoreal product shot, slow zoom on chrome teapot ..."
  ]
}

Heads up — pricing model

PromptVEX is subscription-only. Every plan includes unlimited prompt analysis. Only full-gen renders count against your monthly video allowance. New accounts get 2 free videos to try things out.

Core concepts

Prompt: A natural-language description of the video you want to make. Plain English; you can include camera, lens, lighting, and motion.
Score: An integer 0–100 from Claude. Reflects how unambiguous and renderable the prompt is. Aim for 80+ before a full gen.
Keyframes: Four still frames generated from your prompt at low cost. Use them to confirm composition before paying for motion.
Draft: A 5-second 480p video preview. Confirms motion and timing before a full-resolution render.
Auto-router: PromptVEX picks Kling / Runway / Veo based on motion profile, style, and your remaining allowance.

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