Describe Capabilities

Status: Live (gateway v0.1, stdio). MCP tool: describe_capabilities.

Purpose

Return a machine-readable snapshot of what the execution engine and MCP server support: engine version, gas/trace/bytecode ceilings, named forks, registered EIP capabilities (with query shapes), and seed presets.

When to use

• First call when connecting to the server — learn forks, EIPs, and limits before simulating
• Check whether a specific EIP (e.g. 8024) is registered and which query shapes apply
• Read hard ceilings (max gas, bytecode size, trace steps)

MCP tool name

describe_capabilities

Inputs

None required. Pass {} or omit arguments.

Outputs

Field	Description
engineVersion	Semver of mcp-execution-engine
ceilings	maxGasLimit, defaultGasLimit, maxBytecodeBytes, maxTraceSteps
namedForks	Curated shortcuts (e.g. amsterdam)
eips	Seed capability registry — EIP number, nature, shapes, maturity notes
allowedBaseHardforks	Valid baseHardfork values
presets	Seed compare/simulate preset definitions

Example

Tool call:

{}

Output (abbreviated):

{
  "engineVersion": "0.1.0",
  "ceilings": {
    "maxGasLimit": "30000000",
    "defaultGasLimit": "1000000",
    "maxBytecodeBytes": 24576,
    "maxTraceSteps": 10000
  },
  "namedForks": [{ "id": "amsterdam", "label": "Amsterdam (scheduled EL fork)", "…": "…" }],
  "eips": [{ "eip": 8024, "name": "Backward compatible SWAPN, DUPN, EXCHANGE", "shapes": ["simulate", "compare"], "…": "…" }]
}

JSON schema

describe_capabilities.input.json

Changelog

Describe Capabilities Changelog

1. v0.42026-07-22Live MCP tool page — gateway v0.1 stdio ships describe_capabilities.