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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint=false, so the safety profile is covered. The description adds valuable behavioral context beyond annotations: no auth required, US Gov public domain, base year 2000=100, data range, source dataset, and the specific return categories (total, freight, passenger, plus component indices). No contradictions with 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 sentences front-load the core action first ('Retrieve the BTS Transportation Services Index'), then deliver return contents, base year, date range, source, and auth in order. Every sentence carries useful information with no filler or repetition of schema details.

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?

For a read-only data retrieval tool with rich input schema (100% parameter coverage), output schema present, and strong annotations, the description supplies the remaining context an agent needs: source identifier, auth status, temporal coverage, base year, and return composition. Nothing critical for selecting or invoking the tool is missing.

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 the schema already documents limit, start_date, and end_date with types and defaults. The description's mention of 'monthly' and 'Data from 2000 to present' loosely reinforces the date parameters but adds no new syntactic or format details beyond the schema. 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 states a specific verb and resource: 'Retrieve the BTS Transportation Services Index (TSI)' and clearly defines what the index measures (monthly volume of freight and passenger transportation services across all modes). It distinguishes itself from sibling tools like bts.aviation.traffic and bts.freight.indicators by naming the exact TSI dataset and its component indices.

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 description provides clear context for when to use the tool: it is a monthly economic indicator covering 2000 to present, with total/freight/passenger breakdowns. However, it does not explicitly name alternatives or state when NOT to use it, so an agent must infer its scope against siblings like bts.freight.indicators.

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