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

Annotations already declare readOnlyHint, openWorldHint, and idempotentHint, so the safety profile is covered. The description adds meaningful behavioral context: rental results come as buildings or homes, pagination caps at 1,000 total, and the daysOn sort with sortAscending gives newest first. These go beyond the annotations and help the agent anticipate output structure and sorting semantics.

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 dense but well-organized: core purpose first, then row details, pagination, rental behavior, and sorting. Every sentence carries information; there is no fluff. While it is a bit long, the structure front-loads the most critical usage context and then provides operational details, making it efficient for an agent to parse.

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 tool with 8 parameters and no output schema, the description is remarkably complete. It covers return fields, pagination limits, rental result grouping, sort behavior, and the expand option. It also explains the relationship between location and regionId. Nothing essential for calling the tool correctly is missing, given the detailed schema and annotations.

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%, so each parameter has a description. The description adds extra semantic value by explaining the interaction between sort and sortAscending (daysOn + ascending = newest first), the 1,000-per-search limit (page x pageSize), and the expand option's size implications. These clarifications are not obvious from the schema alone, raising the score above the baseline of 3.

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 (search) and resource (listings) with clear scope: place types (city, ZIP, neighborhood, county) and statuses (for sale, for rent, sold). It distinguishes itself from siblings like zillow_property (single record) and zillow_autocomplete_places (place lookup) by focusing on listing search results. The detail about row fields and pagination further clarifies the tool's exact function.

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 implies when to use this tool: to find listings across multiple statuses and place types. It mentions rental grouping (buildings vs. homes) which hints at edge cases. However, it does not explicitly state when not to use it or name alternative tools (e.g., use zillow_property for a specific zpid). The guidance is clear but lacks explicit exclusions or comparisons to siblings.

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