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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=false, so the safety profile is covered structurally. The description adds genuine value beyond them with the 'nothing is reserved or bought' assurance and by enumerating the response content (carrier, price in BRL, delivery time in business days), which matters since there is no output schema.

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 action and object, then a compact clause describing returned fields, then a short no-side-effect sentence. Two sentences with essentially no filler; the only mild redundancy is repeating 'Brazilian postal code (CEP)', which is already in the schema.

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 four-parameter, read-only quote tool with no output schema, the description covers what is quoted, the units of the values (BRL, business days), the checkout-parity guarantee, and the absence of side effects. An agent has everything needed to select and invoke it correctly.

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 all four parameters (cep, store, quantity, variant_id) are already documented in the schema, including formats and defaults. The description adds only loose context ('a product option', 'Brazilian postal code (CEP)') and no syntax or constraint detail beyond the schema, so the baseline of 3 applies.

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 (quote) and resource (shipping) plus the exact domain of applicability (a product option to a Brazilian CEP). It is unmistakably distinct from find_store, get_product and search_products, which are lookup/browse tools rather than a pricing quote.

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 operating context — it returns the same carrier/price/delivery options the checkout shows, and explicitly notes nothing is reserved or bought. It also implies the prerequisite chain by tying a parameter to the get_product tool, but it never states when to prefer this over, say, a product lookup or what to do if the CEP is invalid.

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