# Farm & Garden Calc – Growing Degree Days (GDD)

> Farm & Garden Calc – Growing Degree Days (GDD) is a paid API for AI agents from agri-calc.x402tookit.com, paid per call via x402, $0.02/call, status unknown (last checked 2026-10-29).

Calculates growing degree days from daily max/min temperatures using either the modified corn 86/50°F method or the standard average method.

## Facts

- Endpoint: GET https://agri-calc.x402tookit.com/gdd?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/farm-garden-calc-growing-degree-days-gdd-90444770
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_dkVybVATxy-6HNiurih0x

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 farm-garden-calc-growing-degree-days-gdd-90444770
```

Example prompt: Calculate growing degree days for my corn crop using the modified 86/50°F method — here are my daily highs and lows for the last week: tmax = 88,85,90,83,79,86,91 and tmin = 55,52,58,50,48,54,57.

## When to prefer this

Choose this endpoint when you need to compute growing degree days from raw daily temperature observations, especially when you want the industry-standard modified corn 86/50°F method with upper and lower temperature clamping. It is ideal for tracking crop phenological development, scheduling agricultural operations, or building season-long GDD accumulation charts from historical or forecast temperature data.

## Known failure modes

- Missing tmax or tmin parameters returns an error
- Mismatched count between tmax and tmin arrays causes failure
- Invalid temperature values or non-numeric strings cause parsing errors
- Unsupported method string (not 'modified' or 'standard') may result in default fallback or error
- Unsupported unit string (not 'F' or 'C') may cause unexpected behavior

## How this service works

Growing degree days from daily max and min temperatures: modified corn 86/50 F method or the simple standard average.

## Output

Returns an array of daily GDD values, a cumulative GDD array, the total accumulated GDD, the method and base/upper temperatures used, the temperature unit, a human-readable summary, and optionally reasons or warnings about the calculation.

## 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": [
      "tmax",
      "tmin"
     ],
     "properties": {
      "base": {
       "type": "number",
       "description": "Base temperature (default 50 F or 10 C)"
      },
      "tmax": {
       "type": "string",
       "description": "Comma-separated daily maximum temperatures"
      },
      "tmin": {
       "type": "string",
       "description": "Comma-separated daily minimum temperatures, same count as tmax"
      },
      "unit": {
       "type": "string",
       "description": "F (default) or C"
      },
      "upper": {
       "type": "number",
       "description": "Upper cutoff for the modified method (default 86 F or 30 C)"
      },
      "method": {
       "type": "string",
       "description": "modified (default: temps clamped into base..upper, the corn 86/50 F method) or standard (plain average minus base, floor 0)"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "properties": {
      "asOf": {
       "type": [
        "null",
        "string"
       ]
      },
      "base": {
       "type": [
        "null",
        "number"
       ]
      },
      "days": {
       "type": [
        "null",
        "number"
       ]
      },
      "unit": {
       "type": [
        "null",
        "string"
       ]
      },
      "upper": {
       "type": [
        "null",
        "number"
       ]
      },
      "method": {
       "type": [
        "null",
        "string"
       ]
      },
      "source": {
       "type": [
        "null",
        "string"
       ]
      },
      "reasons": {
       "type": [
        "array",
        "null"
       ],
       "items": {
        "type": "string"
       }
      },
      "summary": {
       "type": [
        "null",
        "string"
       ]
      },
      "verdict": {
       "type": [
        "null",
        "string"
       ]
      },
      "dailyGdd": {
       "type": [
        "array",
      
… (truncated)
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/farm-garden-calc-growing-degree-days-gdd-90444770/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from agri-calc.x402tookit.com](https://www.zero.xyz/host/agri-calc.x402tookit.com/llms.txt)