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

Annotations already declare read-only, idempotent, non-destructive, open-world behavior, so the safety profile is covered. The description adds non-obvious domain context the annotations cannot: that schema shape varies by year because newer years drop route number/name columns, which is exactly the trap this call exists to avoid.

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?

A single sentence with the purpose front-loaded and the year-schema caveat in a tight parenthetical. No filler or redundant restatement of the title.

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-shape explanation is unnecessary, and the one parameter is fully covered. The description supplies the missing why (year selection before querying) and the column-drift warning; only an explicit pointer to the follow-up tool is absent.

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 `state` parameter is fully documented in the schema (USPS code, 50 states + DC + PR, required because route_id/county_id are state-specific). The description only restates 'for a US state' and adds no syntax or format detail beyond that. Baseline 3 applies.

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?

Names a specific resource (FHWA HPMS data years and per-year columns) scoped to a US state, and the parenthetical explains the concrete variance callers care about (route number/name columns dropped in newer years). It does not name the sibling it precedes (aadt_by_route), so differentiation is implied rather than explicit.

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?

'so callers can pick a year before querying' clearly establishes this as a prerequisite/discovery call that should precede an AADT data query. It gives context but stops short of naming the alternative tool or stating when to skip this step.

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