Pending block

The chain's pending block: how many transactions are queued for the next block, the base fee they will pay, and the gas already used against the limit. Send GET /api/chain/pending with no required fields (2 optional) and pay $0.001 per call over x402 or MPP (there is no free tier). It returns a JSON object with network, number, transactionCount, baseFeePerGas, baseFeePerGasGwei and 4 more.

This is the node's own view of what is about to be mined, so it answers "is the chain congested right now" without an indexer. Transaction hashes are included when the node returns them. EVM chains: ethereum, base, polygon, arbitrum, optimism.

Category: Crypto & onchain data · Tags: evm pending mempool gas rpc · Also found as: mempool pending-block queued

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Parameters

Example request

curl -i "https://agent402.tools/api/chain/pending?network=base"

Without payment this returns HTTP 402 Payment Required with the exact price for chain-pending; any x402 v2 or MPP client pays it and retries.

Example response

{
  "network": "base",
  "number": "34881204",
  "transactionCount": 61,
  "baseFeePerGas": "4218231",
  "baseFeePerGasGwei": "0.004218",
  "gasUsed": "12904331",
  "gasLimit": "150000000",
  "timestamp": "2026-09-12T21:30:11.000Z",
  "note": "A pending block is the node's own view and differs between nodes; it is not a consensus value."
}

From an MCP client

catalog.call {
  "slug": "chain-pending",
  "params": {
    "network": "base"
  }
}

The hosted connector at https://agent402.tools/mcp needs a payment for chain-pending; the stdio package pays it from a wallet or from AGENT402_CREDITS_KEY. Local install: npx -y agent402-mcp.

Errors and behavior

• Every field is optional. An input the tool rejects returns an HTTP 4xx whose body carries error, tool, expected, required and example.
• A paid call that ends in any status of 400 or above is not charged over x402, MPP or a prepaid credits key: settlement is cancelled when the tool fails. The exception is a Tempo push credential, a transfer the buyer sent before the call: it settles before the tool runs, so if the tool then fails the payment is recorded as a refund owed to the paying wallet.
• Wallet-only: this tool reaches the network or stored state, so it has no proof-of-work tier. A prepaid card-credits key issued earlier (Authorization: Bearer a402_...) also pays it.
• A POST with a JSON body to /api/chain/pending is served as this GET, with the body as the input.
• An Idempotency-Key header makes a retried paid call replay the first 200 instead of charging again (an answer larger than 1 MB is not replayed).

Paid call (JavaScript agent)

import { wrapFetchWithPayment } from "@x402/fetch";
import { x402Client } from "@x402/core/client";
import { registerExactEvmScheme } from "@x402/evm/exact/client";
import { privateKeyToAccount } from "viem/accounts";

const client = new x402Client();
client.setSpendControls?.(false); // keep your own spending ceiling in code
registerExactEvmScheme(client, { signer: privateKeyToAccount(KEY) });
const payFetch = wrapFetchWithPayment(fetch, client);

const res = await payFetch("https://agent402.tools/api/chain/pending?network=base");

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