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

No annotations are provided, so the description carries the full burden. It implies a read-only calculation and summarizes the response (enabled services, BRL price, delivery estimate, free shipping), but omits plan-dependent behavior visible only in the schema (Advanced-plan dimension memory), idempotency expectations, and any auth/rate constraints.

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?

Two tightly written sentences with no filler. The purpose and carrier scope come first, and the return summary follows, so the most decision-relevant information is front-loaded.

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 and the input schema is fully annotated, so the description does not need to explain return values or parameter details. It covers what the tool does and what comes back, leaving only usage timing and plan-gated behavior unaddressed.

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 (destinationCep, items, requestId, instanceId) are already documented in detail. The description adds only the framing that items represent a cart; it contributes no new syntax or format meaning beyond the schema. Baseline 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+resource ('Calculate Brazilian Correios shipping rates') and names the carrier services (SEDEX, PAC) plus the input unit ('for a cart'). The siblings (label diagnostics, tracking, label PDFs) are clearly in a different domain, so there is little ambiguity, but the description never explicitly contrasts itself with 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?

There is no statement of when to use this tool versus alternatives, no prerequisites (e.g., must be called before checkout or before generate_label), and no exclusions. 'For a cart' only loosely implies a pre-purchase quoting stage, which is inference rather than guidance.

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