# OpenVerbs Statistics – Pearson Correlation

> OpenVerbs Statistics – Pearson Correlation is a paid API for AI agents from stats.openverbs.com, paid per call via x402, $0.004/call, status unknown (last checked 2026-09-14).

Computes the statistical correlation between two numerical series (x and y arrays)

## Facts

- Endpoint: POST https://stats.openverbs.com/v1/correlation
- Price: $0.004/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/openverbs-statistics-pearson-correlation-c1c8b4b5
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_nyOxdHESe_dLM3T5clgD1

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 openverbs-statistics-pearson-correlation-c1c8b4b5 -d '<json body>'
```

Example prompt: Calculate the correlation between these two numeric series for me: x = [1, 2, 3, 4, 5] and y = [2.1, 3.9, 6.2, 7.8, 10.1]

## When to prefer this

Choose this endpoint when you need a fast, pay-per-call statistical correlation computation without standing up your own math infrastructure. It is ideal for agents that occasionally need to measure linear relationships between two numeric datasets (up to 100,000 points each) without requiring a full data science library or backend. Prefer alternatives if you need batch processing of many pairs simultaneously, non-linear correlation measures (e.g. Spearman), or if you are already running a Python/R environment where scipy or similar is trivially available.

## Known failure modes

- Arrays x and y are different lengths — endpoint requires equal-length arrays
- Array has fewer than 2 elements (minItems: 2) — returns validation error
- Array exceeds 100,000 items (maxItems: 100,000) — payload rejected
- Non-numeric values in either array — schema validation failure
- Network or payment (x402) failure resulting in no response

## How this service works

Pearson correlation coefficient and covariance of two equal-length paired series. Rejected as a clean 400 if the lengths differ or either series has zero variance (correlation undefined).

## Output

A numeric correlation coefficient (typically Pearson's r) representing the strength and direction of the linear relationship between the two input series, ranging from -1 (perfect negative correlation) to +1 (perfect positive correlation), with 0 indicating no linear relationship.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method",
    "bodyType",
    "body"
   ],
   "properties": {
    "body": {
     "type": "object",
     "required": [
      "x",
      "y"
     ],
     "properties": {
      "x": {
       "type": "array",
       "items": {
        "type": "number"
       },
       "maxItems": 100000,
       "minItems": 2,
       "description": "First series."
      },
      "y": {
       "type": "array",
       "items": {
        "type": "number"
       },
       "maxItems": 100000,
       "minItems": 2,
       "description": "Second series (same length as x)."
      }
     },
     "additionalProperties": false
    },
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "POST"
     ],
     "type": "string"
    },
    "bodyType": {
     "enum": [
      "json",
      "form-data",
      "text"
     ],
     "type": "string"
    }
   },
   "additionalProperties": false
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/openverbs-statistics-pearson-correlation-c1c8b4b5/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from stats.openverbs.com](https://www.zero.xyz/host/stats.openverbs.com/llms.txt)