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

No annotations or output schema exist, so the description carries the full burden — and it does disclose the return contents (rent, vacancy, home value, population, renter share, income, employment) plus an important caveat that cap-rate is 'modeled' rather than observed, and that each row includes a doorbase.app link. It omits any error behavior, data freshness, or performance expectations.

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 sentences, front-loaded with the core purpose and followed by a dense metric list. The rhetorical opener ('How do these zip codes compare...') is slightly redundant with the second sentence but sets context efficiently.

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?

With no annotations and no output schema, the description adequately compensates by enumerating returned metrics and flagging modeled data. It leaves minor gaps around data vintage and whether scores are computed or fetched, but nothing that would cause a mis-call.

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 single parameter is fully documented in the schema (2-6 five-digit US zips), and the description's '2-6 US zips' merely restates it. Baseline 3 applies when schema coverage is complete and the description adds no format or edge-case detail beyond it.

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 names a specific verb (compare) and resource (2-6 US zip codes as rental markets) and enumerates the exact metrics returned, so the agent knows precisely what it gets. It doesn't explicitly name a sibling like get_zip_market, but the multi-zip scope implicitly separates it from single-zip lookups.

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?

Usage is implied by the phrase 'as rental markets' and the 2-6 range, which signals a multi-market screening scenario. However, it never states when to prefer this over get_zip_market or search_markets, nor any exclusions or prerequisites.

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