# Crypto Change-Feed Subscription

> Crypto Change-Feed Subscription is a paid API for AI agents from agentdata-api.sander-van-aard.workers.dev, paid per call via x402, $2/call, status unknown (last checked 2026-09-14).

Subscribe to a 30-day change-feed over the crypto signals ledger, returning a handle and cursor for unlimited free polling of new signals, classification flips, and status changes across all coins.

## Facts

- Endpoint: POST https://agentdata-api.sander-van-aard.workers.dev/crypto/feed
- Price: $2/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/crypto-change-feed-subscription-28ca6b78
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_JNtIwWfCuAy1ORKzVCrN-

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-change-feed-subscription-28ca6b78 -d '<json body>'
```

Example prompt: Subscribe me to the 30-day crypto change feed so I can poll for new signals, classification flips, and status changes across all coins — give me back the feed handle and starting cursor.

## When to prefer this

Choose this endpoint when you need continuous, real-time awareness of changes across all crypto signals simultaneously rather than polling individual signals. It is more efficient than per-signal polling (/crypto/poll) when monitoring many coins at once. Prefer this over /crypto/scan for event-driven architectures where you want to react to state changes (new signals, invalidations, score flips) as they happen across the full ledger, without paying per change.

## Known failure modes

- Payment failure: x402 payment not provided or insufficient USDC — subscription not created
- Invalid request body: missing required fields causes 400 error
- Duplicate subscription: attempting to create overlapping subscriptions may return an existing handle
- Upstream ledger unavailable: feed handle issued but cursor may lag behind real-time state
- Polling endpoint (/crypto/feed/since) returns empty if no changes since cursor

## How this service works

Subscribe for 30 days to the change feed behind /crypto/scan: one cursor over the upstream advice ledger, all coins at once. Returns a handle and a cursor; polling is then free and unlimited: /crypto/feed/since returns every published change since your cursor — new signals, classification flips, status changes (PUBLISHED/STALE/INVALIDATED), score and entry-zone changes. Be first to know when the market state flips; the full advice per signal stays a separate paid call.

## Output

Returns a feed_handle (subscription identifier) and an initial cursor. Using the cursor, the agent can then call /crypto/feed/since for free and unlimited polling to retrieve all published changes since that cursor position — including new signals, classification flips, status changes (PUBLISHED/STALE/INVALIDATED), score updates, and entry-zone changes. Full signal advice details require a separate paid call.

## 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-change-feed-subscription-28ca6b78/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)