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

Annotations only declare readOnly/openWorld, but the description adds material behavior the agent cannot infer: paid per-call pricing ($0.002 USDC via x402 on Base/Solana/Arc), the fact that failed calls are not charged, and the weekly publication cadence. Cost-per-call and billing-on-failure are exactly the operational facts an agent needs before invoking.

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?

One dense paragraph, front-loaded with source, subject, and coverage limits, then cadence, then cost. Every clause carries distinct information — scope, exclusion, granularity, price — with no filler or 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 values need not be re-explained, and the description still covers provenance, coverage boundaries, update frequency, and billing behavior. Defaults for week and limit are documented in the schema. Nothing needed to call this correctly 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 coverage is already 100%, so the baseline is 3, but the description adds meaning the schema lacks: destination is limited to '10 major US cities' and truck availability is a 1–5 surplus-to-shortage scale, clarifying what the returned values represent relative to the filters. It does not add syntax or defaults beyond the schema, so it sits above baseline but not at the top.

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+resource with scope: 'Weekly US refrigerated (reefer) truckload spot rates per lane' from USDA AMS/AgTransport. It names the exact fields returned and explicitly excludes adjacent datasets ('not DAT van/flatbed load-board data', 'produce lanes only'), which lets an agent separate it from siblings like dry_van_capacity or spot_freight_rates.

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 clear usage context: weekly cadence, produce lanes only, and an explicit exclusion of DAT van/flatbed load-board data. It stops short of naming which sibling tool to use instead for van/flatbed or non-US rates, so the routing guidance is implicit rather than complete.

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