Web3 EVM Debugger & Auditor MCP

evm_storage_slot_layout_calculator

Calculates exact 32-byte EVM storage slots for nested mappings, dynamic arrays, and packed structs so auditors can verify Solidity state layout per ABI rules.

Instructions

Calculates exact 32-byte EVM storage slots for complex Solidity state variables (nested mappings, dynamic arrays, packed structs) according to ABI specification. (0.035 USDC on Base L2)

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "payload": "<payload>"
    },
    "name": "evm_storage_slot_layout_calculator"
  }
}

Input Schema

Name	Required	Description	Default
`payload`	Yes	Input parameters or JSON string payload for the tool execution
`paymentSignature`	No	Base L2 USDC micropayment signature or transaction hash for x402 settlement

Schema Changelog

Changes observed during successful MCP inspections.

First observedv1.0.0Oct 3, 2026

TDQS

B3.4/5.0

Behavior3/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations, the description carries the behavioral burden. It clarifies that the operation is a calculation following the ABI specification and discloses a fee, but it does not state pure/read-only behavior, input format expectations, or limitations. This is adequate for an obvious calculator but not rich.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The definition is a single front-loaded sentence that immediately states the action and scope, followed by a short parenthetical fee note. There is no filler or redundancy.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness2/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a fairly specialized tool with only a generic 'payload' string parameter and no output schema, the description does not specify what payload structure to send (e.g., variable declarations, slot numbers, mapping keys/array indices) or what the result looks like. An agent could select the tool but would struggle to invoke it correctly.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so the baseline is 3. The description hints that payload should describe complex Solidity state variables, but it does not add concrete syntax or field-level semantics for the generic 'payload' parameter.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description names a specific verb ('Calculates') and a precise resource ('exact 32-byte EVM storage slots') with the scope of complex Solidity state variables including nested mappings, dynamic arrays, and packed structs. This makes it readily distinguishable from EVM sibling tools like decode_evm_calldata or verify_evm_signature.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines2/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

No guidance is given on when to use this tool over alternatives, nor any exclusions or prerequisites. An agent gets no help deciding between this and other storage/ABI/calldata tools; it must infer use from the name and description.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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