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

With no annotations, the description carries the full burden of behavioral disclosure. It covers key behaviors: bidirectional resolution, direction detection, view-specific outputs (profile returns full identity card, avatar dereferences to image URL), and the payment requirement. It also reveals that the tool is paid and explains the two-call settlement mechanism. The only gaps are details like response format or error behavior, which are not critical for selection.

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 compact and front-loaded. The first sentence states the core purpose, the second covers view options, and the third explains the payment flow. Every sentence earns its place with no redundant or filler content. It is easy to scan and extract the key information quickly.

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 complexity (multiple views, paid flow, bidirectional resolution), the description is remarkably complete. It explains the main behaviors, the payment process, and the view alternatives. It omits explicit mention of the 'text' view (only implying it via the keys parameter), but the schema fills that gap. The absence of an output schema is mitigated by the description's clarity about what each view returns.

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 describes all four parameters with examples and clear descriptions, achieving 100% coverage. The description does not add new parameter-level meaning beyond what's already in the schema; it repeats the x_payment flow and view options but does not introduce new semantics. Since the schema already does the heavy lifting, a baseline of 3 is appropriate.

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 opens with a precise statement of what the tool does: resolving an ENS name to an address or an address to its forward-verified primary name. It clearly identifies the resource (ENS names/addresses) and the verb (resolve), and further distinguishes sub-modes via the view parameter. This goes beyond a simple restatement and leaves no ambiguity about the tool's purpose.

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: direction is auto-detected, view options are described, and the paid two-step flow is explicitly explained (call without x_payment to get terms, then call with x_payment). It also names an alternative (the free `pricing` tool) for listing all prices. While it doesn't explicitly state when NOT to use this tool, the context is sufficiently clear for an agent to decide.

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