Run Block

Status: Live on the public MCP. Tool: run_block.

Amsterdam

Run a lab block on Amsterdam with two plain 1 wei transfers — show each receipt.

Look forper-transaction receipts plus the header snapshot

Agent will likely call run_blockWhat you can ask →

Purpose

Run 1–8 impersonated transactions as one lab block and receive a header snapshot plus per-tx receipts. Senders are impersonated from each from — no private key.

This is the verb for a chosen beacon slot (header.slotNumber / EIP-7843), several txs in one block, a lab number / timestamp, or a generic Glamsterdam / Fusaka lab block with no EIP named.

A single paid transfer still belongs on Run Transaction. Raw opcode / stack programs belong on Run Bytecode. Block-level access list JSON belongs on generate_artifact (not this tool).

Agent voice

Tell the user per-transaction paid gas, receipts, and regular-gas deltas in plain language — not transactions[].gasUsed or header field names unless they asked for raw output.

When to use

• “What does SLOTNUM push if the header slot is 42?”
• Two transfers in one Glamsterdam block — receipts in order
• Lab header timestamp or number the EVM can read

MCP tool name

run_block

Inputs

Field	Required	Description
transactions	Yes	1–8 txs. Each has from, to, optional value / data / code / gasLimit
header.slotNumber	No	Beacon slot (decimal). Glamsterdam only
header.number	No	Block number (decimal). Default 1
header.timestamp	No	Unix timestamp (decimal). Default 1
accounts	No	Extra accounts to prefund
fork	No	{ baseHardfork, eips[] } — default glamsterdam

Fork notes

Same named forks as Run Bytecode: default glamsterdam; fusaka when the user asks for current-mainnet EL behavior. One run per named fork unless they ask to compare. slotNumber is rejected on Fusaka.

Outputs

Field	Description
success	Every tx completed without revert or intrinsic failure
gasUsed	Header gasUsed after lab generate (gasUsedScope: block)
header	number, timestamp, gasUsed, optional slotNumber
transactions[]	Per-tx paid gas, optional Glamsterdam txRegularGas / txStateGas, regularGas, recipientPrestate, logs
regularGasDelta	When per-tx regularGas.total differs — part names and values per tx index
error	First tx failure or a block-level catch, else null
provenance	Always present — named eips[] add a compact Spec: clause on caveat

On Glamsterdam, header gasUsed may track the state-gas dimension (EIP-8037). Paid tx gas lives on transactions[].gasUsed.

When two receipts disagree on paid regular gas, explain from regularGas / regularGasDelta — not from matching txStateGas.

Not in this version: BAL JSON, builder requests, historical replay.

Example — first-touch 1 wei (Glamsterdam)

{
  "transactions": [
    {
      "from": "0x00000000000000000000000000000000000000ee",
      "to": "0x00000000000000000000000000000000000000aa",
      "value": "1"
    }
  ],
  "fork": { "baseHardfork": "glamsterdam" }
}

Expected: success: true, transactions[0].gasUsed: "204600", txStateGas: "183600". The same call on fusaka is paid 21000.

JSON schema

run_block.input.json

Limits

Max 8 transactions. See Guarantees for gas ceilings.

Run Block Changelog

Run Block Changelog

1. v0.42026-10-06Public endpoint is live.
2. v0.32026-09-17Fusaka fork note: current-mainnet features, not only a compare baseline.
3. v0.22026-09-16Generic Glamsterdam / Fusaka lab block is a first-class when-to-use.