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

Annotations already declare readOnlyHint, idempotentHint, non-destructive and closed-world, so safety is fully covered. The description adds the payoff: the exact set of metrics and extremes returned, plus the national fallback when state is omitted. It does not mention pagination or precision/rounding, but for a read-only aggregate that is minor.

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, zero waste: the metric inventory is front-loaded and the fallback rule trails immediately after. Every listed item earns its place because no output schema exists to carry that information.

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 takes on the burden of describing returns and does it thoroughly, and it explains the zero-required-parameter case. The remaining gap is sibling disambiguation, which matters given three adjacent FMR tools.

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% and the single parameter's description already says 'Omit for the whole US.' The description's 'Omit state for the national summary' restates that, adding only the word 'national summary' framing rather than new semantics. Baseline 3 is appropriate for a one-parameter tool whose schema is fully documented.

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 the resource (a state's FY 2027 Fair Market Rent picture) and enumerates exactly what the summary contains: county/town counts, median, low/high 2-bedroom FMR, one- and five-year change, and biggest movers. That aggregate framing implicitly separates it from the per-county and per-zip siblings, but no sibling is named 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?

The only usage instruction is 'Omit state for the national summary,' which is parameter guidance rather than tool-selection guidance. Nothing tells the agent when to pick this over compare_fmr, get_fmr_by_county, or get_fmr_by_zip, so the routing has to be inferred from the word 'summary.'

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