evm_sign

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

With no annotations, the description carries the full burden. It discloses private key handling, security risks (MCP logging/conversation history), network-to-chainId mapping, and the return signature format for typed-data. It does not fully specify the returned value for transaction-signing modes, but the security and mode behaviors are well covered.

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

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

The description is longer than typical but every sentence adds useful operational or security context. It front-loads the purpose and enumerates the three actions clearly. The security warning is essential given the sensitive nature of the tool, so length is justified.

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

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

For a complex, security-sensitive EVM signing tool with multiple modes and no output schema, the description covers most key aspects: actions, relevant parameters, network mapping, security caveats, and the typed-data signature return. It omits explicit return value details for broadcast/transaction-signing modes, but overall it is sufficiently complete for an agent to select and call the tool correctly.

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

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

The input schema is empty, so the description must compensate—and it does. It names key parameters (blockchain, network, toAddress, value, gas, fee, domain/types/primaryType/message) and explains network mapping and the private-key parameter convention. It does not provide a full parameter spec, but it gives enough semantic guidance for invocation.

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

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

The description starts with a specific verb+resource: "Sign an EVM transaction or EIP-712 typed-data message." It clearly differentiates from sibling tools (utxo_sign, tron_sign, etc.) by scoping to EVM chains, and further distinguishes three internal operation modes.

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

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

The description provides clear usage context for each of the three modes, including the x402 GASLESS path and how to pass EIP-712 fields verbatim. It does not explicitly compare against sibling tools, but the EVM scope and mode-specific instructions offer strong practical guidance.

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