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

Annotations already declare readOnlyHint and openWorldHint, so the safety profile is covered. The description adds genuinely new behavioral context — the cost of 1 credit and the fact that photos come back inline — which an agent cannot infer from the annotations. It does not mention rate limits, cache behavior, or what happens when a listing is delisted.

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?

Three short sentences, front-loaded with the identity of the tool, followed by return contents and then the invocation rule. No filler and nothing repeated from the title.

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 output schema, the description correctly compensates by listing the returned fields, and it discloses cost. It falls short only on the unexplained `cache_max_age` parameter and the absence of routing guidance against zillow_search.

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 67%; the description supplies the crucial constraint the schema does not express (0 required params): that exactly one of `zpid` or `url` must be passed. The third parameter, `cache_max_age`, is undocumented in both the schema and the description, which is the remaining gap.

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 ("Public details for a Zillow listing") and enumerates the fields returned: price, status, beds/baths, area, address, photo set. This lets an agent tell it apart from zillow_search by implication (single-listing detail vs. search), though it never names that sibling explicitly.

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 only implied: the requirement to supply a `zpid` or `url` scopes the tool to a known listing, which distinguishes it from a search tool. There is no explicit statement of when to use this versus zillow_search or zillow_agent, and no mention of prerequisites or failure modes.

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