Create Webhook

Create a new webhook subscription to receive realtime onchain data.

Creates a new webhook subscription. When creating a webhook, you must specify:

• name: A descriptive name for your webhook
• url: The endpoint where webhook payloads will be sent
• type: The type of events to subscribe to (transactions, activities, or balances)
• addresses: An array of wallet addresses to monitor

Optional Filters

You can narrow down the events you receive by adding optional filters:

• chain_ids: Monitor only specific chains (e.g., [1, 8453] for Ethereum and Base)
• transaction_type: For transaction webhooks, filter by sender or receiver
• counterparty: Filter transactions by counterparty address
• activity_type: For activity webhooks, filter by specific types (send, receive, swap, etc.)
• asset_type: Filter by asset type (native, erc20, erc721, erc1155)
• token_address: Monitor only a specific token contract

Start with broad filters and narrow them down based on your app’s needs. This helps reduce unnecessary webhook deliveries.

Example Use Cases

Monitor USDC Balance Changes

{
  "name": "USDC Balance Monitor",
  "url": "https://example.com/webhooks/usdc",
  "type": "balances",
  "addresses": ["0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045"],
  "chain_ids": [1, 8453],
  "asset_type": "erc20",
  "token_address": "0xa0b86991c6218b36c1d19d4a2e9eb0ce3606eb48"
}

Track All Incoming Transactions

{
  "name": "Incoming Transactions",
  "url": "https://example.com/webhooks/txns",
  "type": "transactions",
  "addresses": ["0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045"],
  "transaction_type": "receiver"
}

Monitor Swap Activities

{
  "name": "Swap Monitor",
  "url": "https://example.com/webhooks/swaps",
  "type": "activities",
  "addresses": ["0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045"],
  "activity_type": "swap"
}

Headers

X-Sim-Api-Key · string · required

Used for authenticating requests. Provide an API key with a purpose of Sim API. See Authentication.

Body

application/json

name · string · required

A descriptive name for the webhook.

url · string<uri> · required

The URL where webhook payloads will be sent.

type · enum<string> · required

The type of onchain event to subscribe to.

Available options:

transactions,

activities,

balances

addresses · string[] · required

List of addresses to monitor.

EVM address.

chain_ids · integer[] | null

Filter events to specific chain IDs. If omitted, all supported chains are included.

transaction_type · enum<string>

ONLY for 'transactions' type webhooks. Filter by sender or receiver. Cannot be used with other webhook types.

Available options:

sender,

receiver

counterparty · string | null

ONLY for 'transactions' type webhooks. Filter transactions by counterparty address.

activity_type · enum<string>

ONLY for 'activities' type webhooks. Filter by specific activity type. Cannot be used with other webhook types.

Available options:

approve,

mint,

burn,

receive,

send,

swap,

call

asset_type · enum<string>

Filter by asset type.

Available options:

native,

erc20,

erc721,

erc1155

token_address · string | null

Filter events to a specific token address.

Response

200

application/json

Webhook created successfully.

id · string<uuid>

The unique identifier for the webhook.

team_id · string

The team ID that owns this webhook.

name · string

A descriptive name for the webhook.

type · enum<string>

The type of onchain event to subscribe to.

Available options:

transactions,

activities,

balances

url · string<uri>

The URL where webhook payloads will be sent.

active · boolean

Whether the webhook is currently active.

created_at · string<date-time>

When the webhook was created.

updated_at · string<date-time>

When the webhook was last updated.

chain_ids · integer[] | null

Filter events to specific chain IDs. If null, all supported chains are included.

transaction_type · enum<string>

For transaction webhooks, filter by sender or receiver.

Available options:

sender,

receiver

counterparty · string | null

Filter transactions by counterparty address.

Example:

"0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045"

activity_type · enum<string>

For activity webhooks, filter by specific activity type.

Available options:

approve,

mint,

burn,

receive,

send,

swap,

call

asset_type · enum<string>

Filter by asset type.

Available options:

native,

erc20,

erc721,

erc1155

token_address · string | null

Filter events to a specific token address.

Example:

"0xa0b86991c6218b36c1d19d4a2e9eb0ce3606eb48"