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

Annotations already declare readOnlyHint, idempotentHint, and non-destructive behavior, so the safety profile is covered. The description adds genuinely useful context beyond that: this is a private, account-scoped resource requiring a browser cookie plus CSRF token, which matters for how an agent must be authenticated. It still omits pagination/return behavior.

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 short sentences, front-loaded, with no filler; both sentences carry information (scope and auth). It is terse rather than padded, though terseness here edges toward under-specification.

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 single-parameter read tool with full schema coverage and annotations covering safety and idempotence, the main gaps are what the tool actually returns and how it relates to sibling listing tools. Given the structured fields carry most of the burden, this is adequate but not complete.

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% and the single 'antes' cursor parameter is fully documented in the schema itself. The description adds no additional meaning about the cursor or filtering, so the baseline 3 for high coverage 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?

"Coleção privada da conta" is a noun phrase that largely restates the name ("meus_compras") rather than stating a verb+resource action like listing or returning the account's purchases. It does not differentiate this tool from near-siblings such as 'salvas', 'compra', or 'salvar_compra', so an agent cannot tell which one actually reads saved purchases.

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 when-to-use or when-not-to-use guidance and no reference to alternatives among the many purchase-related siblings. The only conditional information is the auth prerequisite (account session), which is a precondition rather than usage routing.

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