Web3 EVM Debugger & Auditor MCP

decode_evm_calldata

Decode 4-byte function selectors and EVM calldata into human-readable method signatures, argument types, and named parameters for debugging and auditing.

Instructions

Decodes raw 4-byte function selectors and hex calldata into human-readable method signatures, types, and named arguments. (0.01 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": "decode_evm_calldata"
  }
}

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

B3.1/5.0

Behavior2/5

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

No annotations are provided, so the description carries the full burden. It mentions a payment requirement ('0.01 USDC on Base L2') but doesn't explain the payment flow, whether the tool makes an external call, or what happens if payment fails. It also doesn't disclose any side effects or prerequisites beyond the payment hint.

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

Conciseness4/5

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

The description is a single sentence that front-loads the core function and includes a brief payment note. It's concise and doesn't waste words, though the payment note is oddly placed and could be clearer.

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 tool with no annotations and no output schema, the description is thin. It doesn't explain the payment mechanism, what the output looks like, or any edge cases (e.g., invalid calldata, unsupported selectors). An agent would need more context to invoke it correctly, especially given the payment requirement.

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 schema already documents both parameters. The description adds context about what the payload contains (raw 4-byte selectors and hex calldata) but doesn't explain the paymentSignature parameter beyond what the schema says. Baseline 3 is appropriate since the schema does the heavy lifting.

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

Purpose4/5

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

The description clearly states the tool decodes raw 4-byte function selectors and hex calldata into human-readable method signatures, types, and named arguments. It uses a specific verb and resource, and the mention of 'raw 4-byte function selectors' distinguishes it from sibling tools like verify_evm_signature or decode_revert_reason_hex, though it doesn't explicitly name them.

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

Usage Guidelines3/5

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

The description implies usage for decoding calldata but doesn't explicitly state when to use this tool versus alternatives like decode_revert_reason_hex or verify_evm_signature. The context of '0.01 USDC on Base L2' hints at a payment requirement but doesn't clarify when this tool is the right choice.

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

Deploy Server