# Halowerk Crop Yield NDVI Estimator

> Halowerk Crop Yield NDVI Estimator is a paid API for AI agents from space.halowerk.com, paid per call via x402, $0.003/call, status unknown (last checked 2026-09-14).

Estimates crop yield by computing mean NDVI and an OLS daily NDVI trend from time-series observations, then applying a caller-supplied linear model (intercept + mean_coefficient×mean_NDVI + trend_coefficient×daily_trend).

## Facts

- Endpoint: POST https://space.halowerk.com/v1/crop-yield-ndvi
- 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-crop-yield-ndvi-estimator-2c859856
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_7hr0NrqCIBCEbu8JbUHfr

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-crop-yield-ndvi-estimator-2c859856 -d '<json body>'
```

Example prompt: Using my NDVI observations — day 0: 0.32, day 30: 0.51, day 60: 0.74, day 90: 0.68, day 120: 0.55 — estimate crop yield in tonnes per hectare with an intercept of 1.2, a mean NDVI coefficient of 8.5, and a daily trend coefficient of 150.

## When to prefer this

Choose this endpoint when you already have a pre-validated linear yield model (intercept and coefficients) and a time-series of NDVI values per day after planting, and you need a fast, deterministic yield estimate without invoking a full remote-sensing pipeline. It is ideal for lightweight agronomic dashboards, automated field monitoring agents, or batch yield screening across multiple fields where NDVI data is already available from a separate source.

## Known failure modes

- Fewer than 2 observations provided — validation error
- NDVI values outside [-1, 1] range — schema validation failure
- Missing required coefficients yields mathematically undefined output
- Invalid or missing yield_unit string causes schema rejection
- Poorly calibrated coefficients produce agronomically meaningless estimates with no warning
- Collinear or flat NDVI time series may produce degenerate OLS trend slopes

## How this service works

Computes mean NDVI and an ordinary least-squares daily NDVI trend, then applies yield = intercept + mean_coefficient×mean_NDVI + trend_coefficient×daily_trend. It does not derive NDVI from imagery, account for crop stage or weather, or provide an agronomically calibrated forecast unless the caller supplies valid coefficients.

## Output

Returns the computed mean NDVI across all observations, the OLS-fitted daily NDVI trend slope, and the estimated yield value (intercept + mean_coefficient×mean_NDVI + trend_coefficient×daily_trend) expressed in the caller-specified yield unit. Does not derive NDVI from imagery or apply agronomic calibration beyond the supplied coefficients.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "yield_unit": {
   "type": "string",
   "maxLength": 64,
   "minLength": 1
  },
  "observations": {
   "type": "array",
   "items": {
    "type": "object",
    "required": [
     "day_after_planting",
     "ndvi"
    ],
    "properties": {
     "ndvi": {
      "type": "number",
      "maximum": 1,
      "minimum": -1
     },
     "day_after_planting": {
      "type": "integer",
      "maximum": 10000,
      "minimum": 0
     }
    },
    "additionalProperties": false
   },
   "maxItems": 10000,
   "minItems": 2
  },
  "yield_intercept": {
   "type": "number",
   "maximum": 1000000000000,
   "minimum": -1000000000000
  },
  "yield_per_mean_ndvi": {
   "type": "number",
   "maximum": 1000000000000,
   "minimum": -1000000000000
  },
  "yield_per_daily_ndvi_trend": {
   "type": "number",
   "maximum": 1000000000000000,
   "minimum": -1000000000000000
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/halowerk-crop-yield-ndvi-estimator-2c859856/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from space.halowerk.com](https://www.zero.xyz/host/space.halowerk.com/llms.txt)