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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint=false. The description adds valuable context: reverse records are self-declared and must be forward-resolved before trusting, plus it mentions the API key requirement. This goes beyond the annotations by warning about a security consideration, which is critical for safe usage.

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 a single paragraph that front-loads the core purpose, then covers usage, exclusions, output format, and a caveat. Each sentence adds value, with no redundant fluff. It is slightly long but well-organized and efficient for the information conveyed.

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?

With no output schema, the description fully explains the return JSON fields for both forward and reverse resolutions, addresses the trust caveat for reverse records, and mentions the API key requirement. For a single-parameter tool, it covers everything an agent needs to call it correctly and interpret results safely.

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 schema already describes the 'query' parameter with 100% coverage ('ENS name or 0x-address'). The description reiterates the same information without adding new syntax or format details. It does explain the dual-direction behavior (forward vs reverse), but that is more about output than parameter semantics, so it doesn't elevate beyond the baseline 3.

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?

States a specific verb ('resolve') and resource (ENS names on Ethereum mainnet), clarifies both forward and reverse directions, and explicitly distinguishes itself from other name systems and balances. This differentiates it from siblings like get_balances and other ENS-related tools, making its purpose unambiguous.

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?

Provides explicit when-to-use guidance ('Use it whenever a user gives you a .eth name instead of an address') and names the alternative for balances ('use get_balances with the resolved address'). It also excludes other name systems, leaving no ambiguity about scope.

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