# Grades & Study Calc – Percentile Rank

> Grades & Study Calc – Percentile Rank is a paid API for AI agents from grades-calc.x402tookit.com, paid per call via x402, $0.02/call, status unknown (last checked 2026-10-29).

Calculates the percentile rank of a score within a class list using the mean-rank method, returning rank from top, mean, median, z-score, and surrounding score counts.

## Facts

- Endpoint: GET https://grades-calc.x402tookit.com/percentile-rank?utm_source=zero.xyz
- Price: $0.02/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-29
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/grades-study-calc-percentile-rank-c8bdba19
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_QtybFnvmT6fOyYMPHhHEe

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 grades-study-calc-percentile-rank-c8bdba19
```

Example prompt: My class scores are 55,62,70,73,73,75,78,80,82,85,88,90,91,95 — can you tell me what percentile rank my score of 82 is in, along with the class mean, median, and z-score?

## When to prefer this

Choose this endpoint when you need a statistically grounded percentile rank using the mean-rank method alongside descriptive statistics (mean, median, z-score) for a single score within a known class list. It is ideal for academic grading contexts where the full class score distribution is available and you want more than just a raw rank — particularly when z-score and surrounding counts add context.

## Known failure modes

- Fewer than 2 scores in the comma-separated list returns an error
- Non-numeric values in the scores string cause a parse failure
- More than 500 scores exceeds the class size limit
- yourScore not provided returns a validation error
- Network timeout or x402 payment failure prevents a result

## How this service works

Percentile rank of a score in a class list (mean-rank method), with rank from the top, mean, median and z-score.

## Output

Returns a JSON object with the student's percentile rank (0–100), rank from the top of the class, number of scores above/below/equal to the given score, class size, mean, median, z-score, minimum, maximum, sample standard deviation, a summary verdict, and optional disclaimer or degraded-mode flags.

## 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"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "required": [
      "scores",
      "yourScore"
     ],
     "properties": {
      "scores": {
       "type": "string",
       "description": "Comma-separated class scores, 2 to 500"
      },
      "yourScore": {
       "type": "number",
       "description": "The score to place in the class"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "properties": {
      "asOf": {
       "type": [
        "null",
        "string"
       ]
      },
      "mean": {
       "type": [
        "null",
        "number"
       ]
      },
      "score": {
       "type": [
        "null",
        "number"
       ]
      },
      "median": {
       "type": [
        "null",
        "number"
       ]
      },
      "source": {
       "type": [
        "null",
        "string"
       ]
      },
      "zScore": {
       "type": [
        "null",
        "number"
       ]
      },
      "maximum": {
       "type": [
        "null",
        "number"
       ]
      },
      "minimum": {
       "type": [
        "null",
        "number"
       ]
      },
      "reasons": {
       "type": [
        "array",
        "null"
       ],
       "items": {
        "type": "string"
       }
      },
      "summary": {
       "type": [
        "null",
        "string"
       ]
      },
      "verdict": {
       "type": [
        "null",
        "string"
       ]
      },
      "degraded": {
       "type": [
        "boolean",
        "null"
       ]
      },
      "classSize": {
       "type": [
        "null",
        "number"
       ]
      },
      "disclaimer": {
       "type": [
        "null",
        "string"
       ]
      },
      "notChecked": {
       "type": [
        "array",
        "null"
       ],
       "items": {
        "type": "string"
       }
      },
      "rankFromTop": {
       "type": [
        "null",
        "number"
       ]
      },
      "scoresAbove": {
     
… (truncated)
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/grades-study-calc-percentile-rank-c8bdba19/health.json
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