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

Annotations already cover read-only, idempotent, non-destructive, closed-world behavior, so the bar is lower. The description usefully adds the error behavior for an unknown county and the storage detail that the ratio is stored in hundredths via the site's half-up formula, which is genuine context beyond the annotations.

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 tight sentences with no filler, and the primary subject (what data is stored) is front-loaded. The 'stored hundredths / half-up formula' clause is slightly dense but earns its place by explaining the returned ratio.

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 carries the burden of describing returns, and it does list the fields returned (median rent, renter income, HUD limits, ratio) plus the error case. It could say more about the response shape, but it is sufficient for correct invocation.

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 both parameters are already documented as state name/abbreviation and county name/slug/FIPS with the omit-for-summary rule. The description adds little parameter-level detail beyond that, so the baseline 3 is appropriate.

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 specific data retrieved (Census median rent, renter income, HUD income limits) and the scope (a state or county), so the resource is clear. It does not, however, differentiate itself from the similar sibling lookup_hud_rent, leaving some ambiguity about which lookup to choose.

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 schema's 'omit for the state summary' and the description's note that an absent county returns an error hint at the two modes. There is no explicit when-to-use guidance and no comparison to alternative lookups such as lookup_hud_rent or lookup_covered_market.

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