# Halowerk Thumbnail CTR Bayesian Ranker

> Halowerk Thumbnail CTR Bayesian Ranker is a paid API for AI agents from creator.halowerk.com, paid per call via x402, $0.003/call, status unknown (last checked 2026-09-14).

Updates a shared Beta prior with per-variant click and impression data, then returns posterior means, 95% credible intervals, and a ranking of thumbnail variants by estimated click-through rate.

## Facts

- Endpoint: POST https://creator.halowerk.com/v1/thumbnail-ctr
- Price: $0.003/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/halowerk-thumbnail-ctr-bayesian-ranker-b5a639f4
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_Vx_y7hDjfJTbnJFjjocmq

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 halowerk-thumbnail-ctr-bayesian-ranker-b5a639f4 -d '<json body>'
```

Example prompt: I have three YouTube thumbnails — 'Bold Text' got 1200 impressions and 84 clicks, 'Face Close-up' got 950 impressions and 91 clicks, and 'Minimal Dark' got 600 impressions and 30 clicks. Use a uniform prior and rank them by their estimated click-through rate with 95% credible intervals.

## When to prefer this

Choose this endpoint when you have click and impression counts for multiple thumbnail or creative variants and want a statistically principled ranking using Bayesian Beta-Binomial conjugate analysis. It is especially useful for early-stage experiments with small sample sizes where frequentist p-values are unreliable. Do not use it if you need true A/B test significance testing, causal inference, bias correction, or predictions under distribution shift.

## Known failure modes

- Impressions less than clicks will likely cause validation errors or nonsensical posteriors
- Zero impressions (minimum is 1) will be rejected by schema validation
- Fewer than 1 variant or more than 1000 variants will be rejected
- Prior alpha or beta values outside [0.000001, 1000000] will be rejected
- With very few impressions, credible intervals will be extremely wide and rankings unreliable

## How this service works

Updates one shared beta prior with each variant’s supplied clicks and non-clicks, reports posterior means and bounded normal-approximation 95% intervals, and ranks by posterior mean. It does not run an experiment, correct assignment bias, prove significance or predict future performance under distribution shift.

## Output

Returns an array of variants sorted by their posterior mean CTR, each with: the variant name, posterior mean click-through rate, and lower/upper bounds of a 95% normal-approximation credible interval derived from the Beta posterior. Does not perform hypothesis testing or predict future performance.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "variants": {
   "type": "array",
   "items": {
    "type": "object",
    "required": [
     "name",
     "impressions",
     "clicks"
    ],
    "properties": {
     "name": {
      "type": "string",
      "maxLength": 128,
      "minLength": 1
     },
     "clicks": {
      "type": "integer",
      "maximum": 1000000000000,
      "minimum": 0
     },
     "impressions": {
      "type": "integer",
      "maximum": 1000000000000,
      "minimum": 1
     }
    },
    "additionalProperties": false
   },
   "maxItems": 1000,
   "minItems": 1
  },
  "prior_beta": {
   "type": "number",
   "maximum": 1000000,
   "minimum": 0.000001
  },
  "prior_alpha": {
   "type": "number",
   "maximum": 1000000,
   "minimum": 0.000001
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/halowerk-thumbnail-ctr-bayesian-ranker-b5a639f4/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from creator.halowerk.com](https://www.zero.xyz/host/creator.halowerk.com/llms.txt)