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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false, so safety is covered. The description adds beyond that: 'stable place_id/geography_level fields' and 'source provenance for later property-market evidence packs' clarify output stability and downstream reuse. It does not address error scenarios or rate limits, but the read-only profile is clear.

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 to four sentences with no filler. The first sentence captures purpose, the second enumerates returned fields, and the final gives examples plus an important caveat. It is appropriately front-loaded though slightly longer than absolutely necessary.

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 lists the key returned fields: 'latest level, one-year and five-year change, CAGR, recent direction, stable ident fields, and source provenance.' That is adequate for an analyst to understand the response shape. It does not discuss edge cases like unknown place IDs or mixed geography levels, which would be the next step in completeness.

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 description coverage is 100%, so all six parameters already carry descriptions and enums. The overview's 'two to eight' and 'state, metro, division, national' only repeat what is already in the schema, adding no new parameter-level insight beyond the structured field descriptions.

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?

States a specific verb ('Compare'), resource ('two to eight US geographies'), and the ranking output ('rank them by one-year price-index change'). This clearly separates it from nearby fhfa_hpi_series and fhfa_hpi_trend, whose names imply single-series functions.

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?

Provides explicit usage examples ('compare home-price momentum in Texas and Florida') and a clear exclusion ('Not a property valuation or investment recommendation'). It does not name the sibling alternatives (fhfa_hpi_series/fhfa_hpi_trend) for comparison, but the 'two to eight geographies' condition strongly implies where this tool fits.

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