Whale transaction tracker -- large on-chain transfers with sender, value, USD estimate. Market-moving alerts. Pay-per-call via x402 (USDC on Base L2) -- no API key, no signup, no rate-limit wall.

Part of the klymax402 marketplace -- 100 x402 micropayment APIs for AI agents, one wallet, USDC on Base.

Quickstart -- MCP

Add to your MCP client config (Claude Desktop, Cursor, ElizaOS, etc.):

json

{
  "mcpServers": {
    "whale-alert": {
      "url": "https://whale-alert.api.klymax402.com/mcp"
    }
  }
}

Quickstart -- HTTP (x402)

bash

curl -X POST "https://whale-alert.api.klymax402.com/api/whales" \
  -H "Content-Type: application/json" \
  -d '{}'
# -> 402 Payment Required, with an x402 payment challenge in the response body

Any x402-aware client (@x402/fetch, x402-agent-tools, ATXP) handles the 402 -> sign -> retry cycle automatically.

Tools

Tool	Method	Path	Price	Description
`crypto_track_whale_transactions`	POST	`/api/whales`	$0.008	Track large on-chain whale transactions

`crypto_track_whale_transactions`

Use this when you need to track large on-chain transactions (whale movements) on Ethereum or Base. Returns recent high-value transfers in JSON.

Parameters

Name	Type	Required	Description
`chain`	string	no	Blockchain: 'ethereum' or 'base' (default: ethereum)
`minValue`	number	no	Minimum transaction value in ETH (default: 100)

Returns

transactions -- array of whale transfers sorted by value descending
from -- sender wallet address
to -- receiver wallet address
valueEth -- transaction value in ETH
valueUsd -- estimated USD value at time of transfer
txHash -- transaction hash for on-chain verification
blockNumber -- block number of the transaction
timestamp -- when the transaction occurred

Example response:

json

{"transactions":[{"from":"0xab...","to":"0xcd...","valueEth":500.0,"valueUsd":1552500,"txHash":"0xef...","blockNumber":19845632,"timestamp":"2026-04-13T11:22:00Z"}],"chain":"ethereum","minValue":100,"totalFound":8}

When to use: detecting market-moving whale activity and smart money flows. Essential for trading signal generation and on-chain intelligence.

Not for: wallet balance (use wallet_get_portfolio), token prices (use finance_get_token_price), holder distribution (use token_get_holder_analysis).

Example agent prompts

"Track large on-chain transactions (whale movements) on Ethereum or Base"

Payment

Protocol: x402 -- HTTP-native pay-per-call, no signup, no API key
Network: Base L2 (eip155:8453)
Asset: USDC
Facilitator: Coinbase CDP (primary), PayAI (fallback)
Also reachable via ATXP (OAuth-wrapped x402, RFC 9728 protected-resource metadata)