# HCAD Parcel Value History

> HCAD Parcel Value History is a paid API for AI agents from hcad-api.canvas-cart.workers.dev, paid per call via x402, $0.02/call, status unknown (last checked 2026-09-14).

Returns every tax year's assessed, appraised, and market values for a single Harris County (Texas) parcel by HCAD account number.

## Facts

- Endpoint: GET https://hcad-api.canvas-cart.workers.dev/parcel/:acct/history
- Price: $0.02/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/hcad-parcel-value-history-531fd438
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_AH5VJd6dgsbtnA_lRijzV

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 hcad-parcel-value-history-531fd438
```

Example prompt: Pull the full assessed, appraised, and market value history for Harris County parcel account 0661340000006 — I want to see every tax year on record straight from HCAD.

## When to prefer this

Use this endpoint when you need the complete multi-year valuation history (assessed, appraised, market) for a single Harris County parcel and already have the HCAD account number. It is ideal for year-over-year comparison, tax protest research, and real estate due diligence. Use the companion /search endpoint first if you only have a street address. Prefer this over general real estate APIs when you specifically need raw, authoritative HCAD roll values.

## Known failure modes

- Invalid or non-existent HCAD account number returns an error or empty result
- Account number not in 13-digit format may cause a validation error
- Parcel with no history in HCAD system returns empty array
- Network or worker timeout if HCAD upstream is slow
- Payment failure (x402) if USDC balance is insufficient

## How this service works

Every tax year's assessed, appraised, and market value for one Harris County parcel. Get the acct from GET /search?addr=<street>. Raw HCAD roll values, verbatim, no interpretation.

## Output

A list of records — one per tax year — each containing the assessed value, appraised value, and market value for the specified Harris County parcel, sourced verbatim from the HCAD appraisal roll with no interpretation or transformation.

## 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"
    },
    "pathParams": {
     "type": "object",
     "required": [
      "acct"
     ],
     "properties": {
      "acct": {
       "type": "string",
       "description": "13-digit HCAD account number"
      }
     }
    },
    "queryParams": {
     "type": "object",
     "properties": {}
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object"
    }
   }
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/hcad-parcel-value-history-531fd438/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from hcad-api.canvas-cart.workers.dev](https://www.zero.xyz/host/hcad-api.canvas-cart.workers.dev/llms.txt)