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Crypto Address Activity Watcher
x402
Crypto Address Activity Watcher is a paid API for AI agents from 2s.io, paid per call via x402, $0.125/call, status unknown (last checked 2026-09-14).
Registers a webhook watcher that fires a signed callback whenever a specified crypto address sends or receives funds on Base, Ethereum, or Bitcoin.
Price / call$0.125
Success—
StatusUnknown
How this service works
The (most) everything API: 575+ pay-per-call endpoints for AI agents — ground-truth data, a full AI gateway, and agent infrastructure (storage, queues, watchers). USDC via x402, no signup, no API keys, and upto billing: pay actual usage, not the quote.
Output
Returns a JSON object with ok:true and an array containing the newly created watcher record, including a unique watcherId, current status, the chain and address being watched, direction, assetTypes, minValueUsd, maxFires, firesRemaining, expiry timestamp, a statusUrl to check/cancel the watcher, and the callbackSigner public key used to verify webhook payloads.
Example use cases
Example prompt
“Watch the Ethereum address 0xAbC123...def456 for any incoming ERC-20 token transfers worth at least $50, POST events to https://my-agent.app/hooks/wallet, stop after 50 callbacks, and tag it 'treasury-monitor' so I can identify it later.”
Technical details
Endpoint
POSThttps://2s.io/api/watchers/crypto-address-activityWhen to prefer
Use this endpoint when an AI agent or application needs real-time, event-driven notification of on-chain activity for a specific address — rather than polling a block explorer. Ideal for treasury monitoring, agent payment detection, NFT transfer tracking, or any workflow that must react to blockchain events without manual checking. Prefer over polling-based alternatives when latency matters or when you want to cap callbacks via maxFires.
Side effects
- Invalid or malformed address for the specified chain (EVM vs Bitcoin format mismatch)
- callbackUrl not reachable or malformed
- expiresInSeconds out of range (< 60 or > 7776000)
- maxFires out of range (< 1 or > 1000)
- Payment not included or insufficient USDC via x402
- Unsupported assetType for Bitcoin (only native supported)
- minValueUsd set to 0 or negative (must be > 0)
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| chain | string | Which chain to watch: base, ethereum, or bitcoin. |
| label | string | Optional free-text tag to recognize this watcher later. e.g. "exchange-cold-wallet". |
| address | string | The address to watch — an EVM address (0x… 40 hex) for base/ethereum, or a Bitcoin address (bc1…/1…/3…). |
| payload | object | Arbitrary JSON, echoed back verbatim in every callback so you can route/identify the event on your side. e.g. {"agentId":"a1","reason":"treasury-monitor"} |
| maxFires | integer | Stop after this many callbacks. Default 25, max 1000. The watch ends at whichever comes first — maxFires or expiry. |
| direction | string | Which flows to fire on: "in" = address received, "out" = address sent, "both" = either. Default: both. |
| assetTypes | array | Limit to asset kinds: any of "native" (ETH/BTC), "erc20" (tokens), "erc721" (NFTs). Omit to watch all. EVM only — Bitcoin is always native. e.g. ["erc20"] for token transfers only. |
| callbackUrl | string | Where we POST the event. Any http(s) URL; the JSON body is signed (verify with X-2s-Signature). e.g. https://your-agent.app/hooks/wallet |
| minValueUsd | number | Only fire when the transfer is worth at least this many USD — filters out dust/spam. e.g. 100 ignores anything under $100. Omit to fire on any non-zero amount. |
| expiresInSeconds | integer | How long the watch stays active, in seconds. Default 2592000 (30 days), max 7776000 (90 days). e.g. 86400 = 1 day. |
Tags
x402
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