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

Annotations already declare read-only, idempotent, closed-world behavior, and the description adds real context beyond them: only offers valid today are considered, results are grouped by product, and the tool never sells, reserves, or delivers. The geographic coverage limit is a useful operational constraint not present in structured fields.

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 is front-loaded in the first sentence, followed by freshness, examples, and scope in a tight four-sentence block. Every sentence carries information; no 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?

With an output schema present, the description needn't explain return values, and it covers the things structured fields can't: freshness window, geographic coverage, and the non-transactional nature. Nothing critical for correct invocation is missing, though routing guidance among siblings would complete it.

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 limit, region, category, and alternatives are already documented in the schema. The description only reinforces the region restriction implicitly via the coverage statement and adds nothing about limits, alternative counts, or category usage. 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?

States a specific verb and resource ("Encontra o menor preço de um produto ou tipo de produto") plus the grouping behavior and the cross-market alternatives. It does not explicitly distinguish itself from the closest siblings (compare_product, search_offers, top_deals), so differentiation is left to inference.

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 concrete when-to-use examples ("onde comprar carne mais barato hoje", "menor preço do leite") and a hard when-not constraint (only Joinville/SC, other cities not served). It stops short of naming an alternative tool for the cases it excludes.

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