subscribe_changes
Create a webhook subscription to receive grant-change events matching a filter, with HMAC-signed delivery and x402 payment handling.
Instructions
Create a webhook subscription that pushes grant-change events matching a filter. Cost: $0.20 USDC via x402 (paid by the agent runtime, not the MCP server). On payment failure or missing capability, returns a structured 402 with the payment requirements so the caller agent can satisfy and retry.
Tool call template
Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.
{
"id": 1,
"jsonrpc": "2.0",
"method": "tools/call",
"params": {
"arguments": {
"callback_url": "<callback_url>",
"hmac_secret": "<hmac_secret>",
"filter": "<filter>"
},
"name": "subscribe_changes"
}
}Input Schema
| Name | Required | Description | Default |
|---|---|---|---|
| filter | Yes | ||
| ttl_days | No | ||
| hmac_secret | Yes | Shared secret used to HMAC-SHA256 sign delivery payloads | |
| callback_url | Yes | HTTPS URL that receives POSTed events |