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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), so the description's added value is the auth context: financials:read scope, read risk, no side effects, and a clear statement that the tool is unavailable when the scope is not granted. That availability caveat is information the agent could not get from annotations or 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?

One purpose sentence followed by a tight metadata line (scope, risk, effects, availability) — front-loaded and free of repetition. The metadata block is boilerplate but each item earns its place.

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 two-parameter read tool with full schema coverage and rich annotations, the essentials are present, including the blocking availability status. However, with no output schema the description never indicates what a 'saldo devedor' record contains (per-stay total? open invoice detail?), leaving the return shape unexplained.

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 both date parameters document their defaults (start/end of current month), so the schema carries the parameter burden. The description adds only the vague 'no período' hint, with no format or inclusive/exclusive-boundary detail beyond the schema.

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?

The first sentence names the resource and the filter precisely: active or closed stays that still carry an open balance within the period. An agent can tell it apart from payment- or bill-listing siblings by the 'saldo em aberto' framing, though no sibling is named explicitly.

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?

Usage is only implied by the content description ('no período' plus outstanding-balance scope); there is no explicit when-to-use, no when-not, and no routing to alternatives such as list_guest_bills or list_payments. The unavailability notice does tell the agent it cannot be called under the current authorization, which is useful but is not selection guidance.

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