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

Annotations already declare readOnly/idempotent/non-destructive/openWorld, but the description adds substantive behavior: cost (free, no plan credits), failure semantics ('reported as not found, never guessed'), coverage limits (US only; PO boxes and rural routes often fail), and a sources[] array in every response. That is real context beyond the structured fields.

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?

Well front-loaded: the core transformation is in sentence one and constraints follow. It is somewhat bloated for a one-parameter tool, repeating the free/no-credits claim three times across separate sentences, which is wasted space.

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?

An output schema exists, so return-value detail is unnecessary, yet the description still flags the sources[] element. Combined with cost, failure behavior and geographic limits, an agent has everything needed to call this 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?

Schema coverage is 100% and the single address parameter is already documented with an example, so baseline is 3. The description adds real constraint meaning for that parameter — US-only scope and PO-box/rural-route non-match behavior — which helps the agent predict failures, though it gives no syntax or normalization guidance.

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 and resource ('turns a US street address into a latitude/longitude plus the state, county and census tract ... with GEOIDs') and names the mechanism (U.S. Census Bureau geocoder). It clearly separates itself from siblings by noting that flood_zone, hazard_history and address_profile also accept addresses directly.

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?

Gives explicit sequencing ('Use it first, then pass the point to the paid property tools') and an explicit when-not: 'call this only when the user wants the location itself.' Alternatives are named, so the agent can route correctly without inference.

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