EVM MCP Server

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

Annotations provide idempotentHint=true and destructiveHint=false, but the description adds valuable context: it explains the signature's verification scope ('on-chain or off-chain') and mentions the wallet configuration dependency. However, it doesn't detail potential side effects like gas costs or security implications, leaving some behavioral aspects uncovered.

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 front-loaded with the core purpose, followed by use cases and verification details in two efficient sentences. Every phrase adds value without redundancy, making it highly concise and well-structured for quick comprehension.

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?

Given the tool's moderate complexity (signing operation with cryptographic implications), no output schema, and rich annotations, the description is mostly complete. It covers purpose, usage, and verification but lacks details on error cases or response format, which could enhance completeness for an AI agent.

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?

Schema description coverage is 100%, with the parameter 'message' fully documented in the schema. The description adds no additional parameter details beyond what the schema provides, such as format examples or constraints, so it meets the baseline for high schema coverage without extra value.

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 clearly states the specific action ('Sign an arbitrary message') and resource ('using the configured wallet'), distinguishing it from sibling tools like sign_typed_data (which handles structured data) and other read/write operations. It precisely defines the tool's function without ambiguity.

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 explicitly lists three use cases: 'authentication (SIWE), meta-transactions, and off-chain signatures,' providing clear guidance on when to use this tool. It also implicitly distinguishes it from sign_typed_data by focusing on arbitrary messages rather than structured data, though it doesn't explicitly name alternatives.

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