# LaunchCheck Reaction Check

> LaunchCheck Reaction Check is a paid API for AI agents from launchcheck-x402.fly.dev, paid per call via x402, $0.5/call, status unknown (last checked 2026-09-14).

Stress-tests launch copy through eight audience lenses and returns structured risks, likely questions, recommended changes, and a fact-preserving rewrite.

## Facts

- Endpoint: POST https://launchcheck-x402.fly.dev/v1/reaction-check
- Price: $0.5/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/launchcheck-reaction-check-84747aa6
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_4-54Wf_CakeWwf0Ci90Gg

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability launchcheck-reaction-check-84747aa6 -d '<json body>'
```

Example prompt: Can you stress-test the landing page copy I wrote for my new project management tool — my target audience is startup CTOs, the desired action is signing up for a free trial, and here's the copy: [paste copy]. I want to know what risks, objections, and questions different audiences might have, plus a rewrite that preserves all the facts.

## When to prefer this

Choose this endpoint when you need structured, multi-lens critique of marketing or launch copy before publishing — especially when you want both diagnostic feedback (risks, objections, questions) AND an actionable rewrite in a single call. Prefer it over generic LLM prompts when you need consistent structured output across eight audience perspectives, and over human copywriters when speed and cost matter. Best suited for landing pages, product announcements, changelogs, pricing pages, app store listings, and launch emails.

## Known failure modes

- Content too short (under 40 characters) returns validation error
- Content exceeds 12,000 character limit returns rejection
- More than 10 constraints provided returns validation error
- Invalid contentType enum value returns schema validation error
- Payment failure via x402 protocol returns 402 with payment details
- Ambiguous or very generic copy may produce low-signal generic recommendations

## How this service works

Review and stress-test launch messaging, landing pages, product announcements, pricing pages, changelogs, app-store listings, and marketing emails before publication. LaunchCheck evaluates copy through eight audience lenses, surfaces positioning and conversion friction, flags claims needing evidence, predicts likely reader questions, recommends concrete changes, and returns a fact-preserving rewrite.

## Output

Returns structured output including: a list of risks identified across eight audience lenses, likely questions those audiences would ask, specific recommended changes to the copy, and a fact-preserving rewrite of the original content.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "content": {
   "type": "string",
   "maxLength": 12000,
   "minLength": 40,
   "description": "Launch or marketing copy to review before publication, such as a landing page, product announcement, changelog, pricing page, app-store listing, or email."
  },
  "constraints": {
   "type": "array",
   "items": {
    "type": "string",
    "maxLength": 300,
    "minLength": 1
   },
   "default": [],
   "maxItems": 10,
   "description": "Optional factual, legal, brand, or wording constraints that the review and rewrite must preserve."
  },
  "contentType": {
   "enum": [
    "landing-page",
    "product-announcement",
    "changelog",
    "pricing-page",
    "app-store-listing",
    "email",
    "other"
   ],
   "type": "string",
   "default": "other",
   "description": "Kind of copy being reviewed; use other when none of the listed categories fit."
  },
  "desiredAction": {
   "type": "string",
   "maxLength": 500,
   "description": "Optional action the copy should persuade the reader to take, such as sign up, start a trial, buy, upgrade, or learn more."
  },
  "productContext": {
   "type": "string",
   "maxLength": 2000,
   "description": "Optional context about the product, feature, offer, or company needed to judge positioning, clarity, and factual fit."
  },
  "targetAudience": {
   "type": "string",
   "maxLength": 1000,
   "description": "Optional intended audience or buyer segment whose likely reaction should inform the review."
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "meta": {
   "model": "example-model",
   "cached": false,
   "engine": "openai-compatible",
   "generatedAt": "2026-07-26T12:00:00.000Z"
  },
  "report": {
   "score": 74,
   "verdict": "revise",
   "topRisks": [
    {
     "fix": "State the specific pre-launch decision the review helps make.",
     "title": "Differentiation is vague",
     "evidence": "The copy lists checks without explaining why they beat a generic critique.",
     "severity": "medium",
     "whyItMatters": "Readers may not see why the specialized review is worth using."
    }
   ],
   "inputIntegrity": {
    "status": "clean",
    "evidence": []
   },
   "likelyQuestions": [
    "Why use this instead of a generic model?"
   ],
   "requiredChanges": [
    "Clarify the specialized value."
   ],
   "executiveSummary": "Clear value, but the differentiation needs stronger evidence.",
   "suggestedRewrite": "Stress-test launch copy before you publish with eight audience lenses, evidence checks, concrete fixes, and a fact-preserving rewrite.",
   "audienceReactions": [
    {
     "lens": "Skeptical technical buyer",
     "friction": "Differentiation is unclear.",
     "reaction": "mixed",
     "confidence": 0.82,
     "likelyThought": "Useful, but why not use a generic model?"
    },
    {
     "lens": "Busy nontechnical decision-maker",
     "friction": "Differentiation is unclear.",
     "reaction": "mixed",
     "confidence": 0.82,
     "likelyThought": "Useful, but why not use a generic model?"
    },
    {
     "lens": "Price-sensitive solo user",
     "friction": "Differentiation is unclear.",
     "reaction": "mixed",
     "confidence": 0.82,
     "likelyThought": "Useful, but why not use a generic model?"
    },
    {
     "lens": "Privacy and security-conscious evaluator",
     "friction": "Differentiation is unclear.",
     "reaction": "mixed",
     "confidence": 0.82,
     "likelyThought": "Useful, but why not use a generic model?"
    },
    {
     "lens": "Existing customer scanning for regressions",
     "friction": "Differentiation is unclear.",
     "reaction": "mixed",
     "confidence": 0.82,
     "likelyThought": "Useful, but why not use a generic model?"
    },
    {
     "lens": "First-time visitor with low context",
     "friction": "Differentiation is unclear.",
     "reaction": "mixed",
     "confidence": 0.82,
     "likelyThought": "Useful, but why not use a generic model?"
    },
    {
     "lens": "Enthusiastic early adopter",
    
… (truncated)
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/launchcheck-reaction-check-84747aa6/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from launchcheck-x402.fly.dev](https://www.zero.xyz/host/launchcheck-x402.fly.dev/llms.txt)