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eth_eoa_address

Derive an EOA's Ethereum address and public key from its private key.

Instructions

Derive an EOA's Ethereum address and public key from its private key.

The public key is the curve point k*G, serialized uncompressed (0x04 || X || Y); the address is the last 20 bytes of keccak256(X || Y), EIP-55 checksummed. This is the externally-owned-account counterpart to eth_contract_address — it derives, it does not create an account. Returns {address, public_key}; the private key is never echoed back.

Exactly one of private_key (inline hex) or private_key_file (a path the server reads, which keeps the key out of the conversation) is required.

Example: eth_eoa_address( "0xac0974bec39a17e36ba4a6b4d238ff944bacb478cbed5efcae784d7bf4f2ff80") -> address="0xf39Fd6e51aad88F6F4ce6aB8827279cffFb92266".

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
private_keyNoA 32-byte secp256k1 private key as hex (0x prefix optional). Never echoed back in the result. Give this or `private_key_file`.
private_key_fileNoPath of a file holding the private key as 64 hex digits (0x and surrounding whitespace optional) or as 32 raw bytes; `~` is expanded. The server reads the file itself, so the key appears in neither the call nor the result, and no error quotes the file's contents. Give this or `private_key`.

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed6 schema fields changedv0.4.1
    • addedInput schema / properties / private_key / anyOf
      Added value: +[
+  {
+    "type": "string"
+  },
+  {
+    "type": "null"
+  }
+]
    • addedInput schema / properties / private_key / default
      Added value: +null
    • changedInput schema / properties / private_key / description
      Previous value: -"A 32-byte secp256k1 private key as hex (0x prefix optional). Never echoed back in the result."New value: +"A 32-byte secp256k1 private key as hex (0x prefix optional). Never echoed back in the result. Give this or `private_key_file`."
    • removedInput schema / properties / private_key / type
      Removed value: -"string"
    • addedInput schema / properties / private_key_file
      Added value: +{
+  "anyOf": [
+    {
+      "type": "string"
+    },
+    {
+      "type": "null"
+    }
+  ],
+  "default": null,
+  "description": "Path of a file holding the private key as 64 hex digits (0x and surrounding whitespace optional) or as 32 raw bytes; `~` is expanded. The server reads the file itself, so the key appears in neither the call nor the result, and no error quotes the file's contents. Give this or `private_key`.",
+  "title": "Private Key File"
+}
    • removedInput schema / required
      Removed value: -[
-  "private_key"
-]
  2. Addedv0.4.0

TDQS

A4.4/5.0
Behavior4/5

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

With no annotations, the description carries the load and does so well: it discloses the return shape ({address, public_key}), guarantees the private key is never echoed back, and notes that file-based keys appear in neither call nor result and are never quoted in errors. It could still mention error behavior for invalid keys, but the security-relevant traits are covered.

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?

Front-loaded with the core purpose, then derivation detail, sibling comparison, and an example. It is on the longer side but each sentence carries distinct value; no obvious filler.

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

Completeness5/5

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

No output schema exists, yet the description specifies the return object, the key-exclusion guarantee, the exact-one-of parameter constraint, and a worked example — everything an agent needs to call it correctly.

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

Parameters4/5

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

Schema coverage is already 100%, so the baseline is 3; the description adds the mutual-exclusivity rule ('Exactly one of private_key or private_key_file is required') plus the rationale for the file variant (keeps the key out of the conversation), which goes beyond the schema.

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?

States a precise verb+resource: 'Derive an EOA's Ethereum address and public key from its private key.' It explicitly distinguishes itself from the sibling `eth_contract_address` as the EOA counterpart, so an agent can pick between them without opening schemas.

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

Usage Guidelines4/5

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

Gives clear context ('derives, it does not create an account') and names the sibling it parallels, which helps route selection. It stops short of an explicit when-to-use/when-not statement against a concrete alternative scenario, so it is not a full 5.

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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