Get Zestimate history for a property

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

Beyond the readOnlyHint and idempotentHint annotations, the description discloses that rent values are conditionally included, that empty `points` may indicate a rendering limitation rather than absence of history, and that an explanatory `note` is returned in that case. It also reiterates that the tool is read-only and safe to call repeatedly, adding useful behavioral context.

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 compact yet information-dense, front-loading the core behavior and output format before addressing the edge case. Every sentence adds value—either clarifying the return structure, guiding tool selection, or explaining empty results—so nothing is wasted.

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?

Given that there is no output schema, the description adequately explains the return format (time series of {date, value, rent?}), the conditional rent inclusion, and the empty-points note behavior. It also covers parameter choice and read-only safety, leaving no critical gap for an agent to call and interpret the tool correctly.

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 input schema fully documents both parameters with clear descriptions ('Provide either zpid or url'). The description only restates the 'zpid or homedetails URL' selection without adding new semantic information, so the baseline of 3 is appropriate because schema coverage is 100%.

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 clearly states the tool returns historical Zestimate values for a property by zpid or homedetails URL, and describes the output as a time series. It explicitly distinguishes itself from the sibling zillow_get_property, which returns only the current Zestimate as a scalar, so an agent can immediately tell the tools apart.

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 gives explicit guidance on when to use this tool: 'call this tool when you need the trend.' It contrasts with zillow_get_property and even explains an edge case where `points` is empty due to client-side rendering versus a genuine no-history scenario, which helps the agent interpret a non-obvious result.

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