# Crypto Signal Change Check (Lightweight Poll)

> Crypto Signal Change Check (Lightweight Poll) is a paid API for AI agents from agentdata-api.sander-van-aard.workers.dev, paid per call via x402, $0.01/call, status unknown (last checked 2026-09-14).

Polls whether a previously retrieved crypto opportunity signal has changed since a known version, returning change types, live status, and next-check timing — without resending the full payload.

## Facts

- Endpoint: POST https://agentdata-api.sander-van-aard.workers.dev/crypto/check
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/crypto-signal-change-check-lightweight-poll-c0bc2da0
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_isEEy1d0HiAJC-xjwNEL4

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 crypto-signal-change-check-lightweight-poll-c0bc2da0 -d '<json body>'
```

Example prompt: Check whether crypto signal abc123 has changed since version 7 — tell me its current status and what specifically changed, like score, entry zone, or execution blockers.

## When to prefer this

Choose this endpoint when you have already retrieved a full crypto signal via /crypto/verdict or /crypto/signal and need to efficiently monitor it over time without paying for repeated full-payload fetches. It is strictly cheaper and faster than re-calling the full signal endpoint. Use it in polling loops where bandwidth and cost matter. Do not use it as your first call — you need a valid signal_id and known_version first.

## Known failure modes

- Unknown signal_id returns a not-found error
- Missing required fields (signal_id or known_version) returns a validation error
- Payment not attached or insufficient returns HTTP 402
- Upstream signal system unavailable may return a 503 or timeout
- Stale known_version that predates system history may return an error or force a full re-fetch

## How this service works

Cheap polling for a crypto opportunity you already retrieved: send signal_id plus the known_version you hold and receive whether it changed, the current version, live status (ACTIVE/STALE/INVALIDATED), which change types occurred (score, classification, entry zone, economics, execution blockers, status) and next_check_after — no full signal payload. Built for monitoring an active opportunity over time. Market intelligence only: no execution, no custody, no position sizing. Paid per request.

## Output

Returns a changed boolean, the current version number, live status (ACTIVE, STALE, or INVALIDATED), an array of change type labels (e.g. score, classification, entry_zone, economics, execution_blockers, status), and a next_check_after timestamp indicating when to poll again. No full signal payload is included.

## 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"
    },
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "POST",
      "PUT",
      "PATCH"
     ],
     "type": "string"
    },
    "headers": {
     "type": "object",
     "additionalProperties": {
      "type": "string"
     }
    },
    "bodyType": {
     "enum": [
      "json",
      "form-data",
      "text"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "additionalProperties": {
      "type": "string"
     }
    }
   },
   "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/crypto-signal-change-check-lightweight-poll-c0bc2da0/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from agentdata-api.sander-van-aard.workers.dev](https://www.zero.xyz/host/agentdata-api.sander-van-aard.workers.dev/llms.txt)