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

Annotations already declare readOnlyHint, openWorldHint, and idempotentHint. The description adds useful behavioral context beyond those annotations by stating what fields are returned, including the exact bounding rectangle search uses. It does not contradict the annotations.

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, with no filler or redundant explanation. The em-dash structure is slightly awkward, but every segment contributes useful information about purpose, output, or input.

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 simple, read-only lookup with no output schema and fully documented parameters, the description adequately covers what the tool returns and how to invoke it. It does not discuss failure or ambiguity behavior when a place name does not resolve, but that is a minor gap given the tool's simplicity.

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 coverage is 100% and the schema already describes both location and regionId, including the anyOf relationship. The description's 'Give location or regionId' only restates this relationship and adds no new parameter-level meaning.

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 tool resolves a place name to a Zillow region and enumerates the returned data: id, type, parent state and city, centre, and the bounding rectangle used by search. It also covers the reverse path, describing a region given a regionId. It does not explicitly differentiate itself from sibling tools, so it falls short of a 5.

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 imperative 'Give location or regionId' offers invocation guidance, and the lookup purpose implies when it would be appropriate. However, there is no explicit when-to-use versus sibling tools like zillow_autocomplete_places or zillow_property, and no mention of caveats or exclusions.

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