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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), and the description still adds meaningful context beyond them: no API key required, reports publish twice monthly and are fetched on the 1st/15th, so data can be roughly two weeks stale. The staleness disclosure is exactly the kind of trait an agent needs and cannot infer from 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?

Purpose and source are front-loaded, and every sentence carries distinct information (alternatives, auth, refresh cadence, return shape). It is somewhat dense with parenthetical detail, but no sentence is filler.

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?

No output schema exists, but the description compensates by naming the return components (price, unit typically USD per ton, change vs prior report) alongside freshness expectations. An agent has everything needed to call and interpret this single-parameter lookup.

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% with a single enumerated product slug, so the schema fully documents the parameter. The description adds no per-parameter syntax or format guidance beyond the schema, which is the expected baseline here.

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 ('Latest price for one fertilizer product') with source (USDA MARS production cost reports) and scope (Illinois-led regional coverage). It explicitly distinguishes itself from get_fertilizer_history (time-series extension) and get_spreads (cost-relation view), so an agent can route without opening schemas.

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 a direct when-to-use ('current input-cost quote') and names the alternative for a different need ('use get_spreads instead to relate fertilizer cost to corn or cattle prices'). Both the selection condition and the exclusion are explicit.

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