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

Annotations already cover the safety profile (read-only, idempotent, non-destructive, closed-world), so the bar is lower. The description still adds real context: the data source (SEC filings), fuel surcharges included, the backtest qualification on the outlook, and notably 'Does not count toward the allowance', a quota disclosure.

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?

Front-loaded with the core outcome, and each clause (source, surcharge treatment, backtest, omit behavior, national scope, allowance) earns its place. It is dense as one long sentence but not padded.

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 usefully characterizes the returned quantity (YoY change in revenue per carload) and scope. For a one-param read tool this is nearly complete; only the exact return shape/pagination is left implicit, which is minor.

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 enum param is fully documented in the schema, so the schema carries the load. The description restates the group choices and the omit-for-both behavior without adding format or edge-case meaning beyond it — baseline 3.

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?

It states a specific verb and resource — how U.S. rail carload prices are moving, measured as Class I revenue per carload YoY from SEC filings. The scope ('National, not lane-specific', Agricultural/Industrial freight) clearly separates it from lane-level siblings like estimate_rail_rate and from the broader get_market_outlook.

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?

There is clear context: 'Omit the group to get both' and 'National, not lane-specific' guide invocation and implicitly rule out lane-level use. It stops short of naming an explicit alternative (e.g., estimate_rail_rate) for the lane-specific case, so it is short of a 5.

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