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

Annotations already declare readOnlyHint=true, openWorldHint=true, and idempotentHint=true, so the agent knows this is a safe, non-mutating operation. The description adds only that it returns Zillow's list of nearby homes, with no additional traits like sorting or pagination. This doesn't contradict annotations, but it also doesn't add significant behavioral context beyond them.

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 sentence that front-loads the purpose and output fields, with zero filler or redundancy. It is concise without sacrificing clarity.

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?

This is a simple read-only tool with one required parameter and full schema coverage. The description lists all key output fields, and annotations cover safety and idempotency. While it doesn't mention response shape details like list ordering or expand behavior, those are not critical for a tool this simple and are partially inferable from the 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%: both zpid and expand have clear descriptions in the input schema. The tool description does not add parameter-level meaning, but the schema carries that weight, so the 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 states a specific verb and resource: it returns homes Zillow shows near a given property, listing zpid, address, price, beds, baths, living area, and status. The phrase 'near this one' differentiates it from search_listings and comps, though it doesn't explicitly name a sibling.

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?

There is no explicit guidance on when to use this tool versus zillow_comps or zillow_search_listings. The description implies usage through 'near this one' but lacks any when-not-to-use context or alternative routing.

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