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

Annotations already cover read-only, idempotent, and open-world behavior. The description goes beyond them by disclosing the output shape (region id, type, centre) and the kind of data Zillow knows (cities, ZIPs, neighborhoods, counties). This is genuinely useful since there is no output schema, and it does not contradict any annotation.

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?

Two tight sentences with no filler. The first sentence defines the tool and its result; the second situates it in the search flow. Every phrase earns its place.

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 an autocomplete-style lookup with annotated safety, the description is complete: it covers input intent, result contents, and how the result should be used downstream. The schema covers parameters, and the description covers the missing output-shape context that would normally come from 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?

Schema description coverage is 100%, so the parameter meanings are already fully documented in the schema. The description adds a little semantic color by naming the region types, but it does not materially improve on the existing parameter descriptions.

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 identifies the resource exactly: regions known for a partial place name, including the concrete outputs (region id, type, centre). It also differentiates the tool from nearby siblings by framing it as the prerequisite for zillow_search_listings and the path to a regionId.

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 phrase 'What a search box needs before zillow_search_listings, and the way to a regionId' gives clear contextual guidance on when to use this tool. It names a related sibling and the intended flow, though it does not explicitly state when not to use it or list alternative tools.

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