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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), and the description adds genuinely useful behavior beyond them: the data is USDA weekly, the outlook is only produced 'where it has passed a backtest,' it reports when places aren't on a priced corridor, and it 'does not count toward the allowance.' That quota/backtest/edge-case disclosure is strong context, though return format and staleness are still unstated.

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, front-loaded with what the tool returns, followed by the outlook condition, the failure case, and the quota note. Every sentence earns its place with no padding.

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 two-parameter read tool with strong annotations but no output schema, the description covers data source, cadence, the outlook caveat, an error path, and billing impact. It stops short of describing the returned fields or units, which is the only notable gap given no output schema exists.

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%, so origin/destination are already documented. The description nonetheless adds a real constraint the schema lacks: the places must lie on the Mississippi, Illinois, or Ohio River corridor, which directly shapes valid values for both parameters.

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 ('USDA weekly downbound grain barge rates') plus the exact scope (two Mississippi/Illinois/Ohio River places). This distinguishes it from estimate_barge_rate (a point estimate) and the broader get_market_outlook/get_rail_market_outlook siblings without needing to name them.

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 never says when to reach for this tool versus estimate_barge_rate or the other outlook tools, and names no alternatives or exclusions. The sentence about unpriced corridors describes behavior, not usage selection, so the agent is left to infer the context.

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