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

Annotations already declare readOnly, idempotent, open-world and non-destructive, so safety is covered. The description adds real value beyond them by enumerating the returned measures (latest level, 1y/5y change, CAGR, direction, stable place_id/geography_level, provenance) and stating the ranking behavior. No auth, rate-limit, or pagination context is offered.

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?

Four sentences, front-loaded with the action and scope, then returns, then example use cases, then the boundary. Each sentence contributes distinct information and nothing is redundant.

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 carries the return-value burden by listing the measures produced. Annotations cover the safety profile, parameters are fully documented, and both positive and negative usage boundaries are stated. Nothing essential for correct invocation is missing.

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 baseline is 3. The description adds meaning by framing the call as operating 'on a consistent FHFA HPI series', implying frequency/flavor/basis apply uniformly across all requested places, which the schema does not state. It also reinforces the 2-8 cardinality constraint.

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 gives a specific verb+resource (compare US geographies on a consistent FHFA HPI series) plus scope (two to eight) and the ranking key (one-year price-index change). It strongly differentiates from single-series siblings like fhfa_hpi_series by virtue of the multi-geography comparison, but it never names those siblings 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?

Two concrete example invocations ('compare home-price momentum in Texas and Florida', 'which of these metros has stronger five-year appreciation?') plus a negative exclusion ('Not a property valuation or investment recommendation') make the intended use clear. It stops short of naming an alternative tool for the excluded cases, so 5 is not warranted.

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