ens-lookup

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

The description lists all the fields returned (address, ens_primary, avatar_url, etc.), providing good transparency on the tool's output. Since no annotations are provided, the description carries the full burden; it does not mention rate limits or authentication, but for a read-only lookup tool, this is sufficient.

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 concise with two sentences, front-loading the core purpose and immediately providing usage variants. Every sentence adds value without redundancy.

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 simplicity (one parameter, no output schema), the description completely covers what the tool does, when to use it, and what to expect in return. The list of returned fields compensates for the lack of an output schema.

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 covers the single parameter 'name' with 100% description coverage, so baseline is 3. The description adds value by explaining how the parameter is used differently for forward vs reverse lookups, enhancing understanding beyond the schema.

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 explicitly states 'ENS name ↔ Ethereum address resolution' and details both forward and reverse lookup operations, making the purpose very clear. It distinguishes itself from sibling tools by focusing specifically on ENS resolution.

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 tells the agent when to use the tool: pass a .eth name for forward lookup or a 0x address for reverse lookup. While it doesn't explicitly mention when not to use it or provide alternatives, the context is clear enough for correct usage.

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