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

Beyond the annotations, the description discloses useful behavior: the upstream returns one row per (numeroItem, unidade, tipo), repeated numeroItem values are not duplicates, a `resumo_por_item` aggregation is attached to avoid ambiguity, and there is a 15-minute cache because balance changes throughout the day.

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?

The description is well-structured, front-loaded with the main purpose, and uses tight sections for complexity, risk context, payload shape, aggregation, and cache behavior. It slightly overshoots with an internal provenance note ('achado bateria A v0.3.5') that carries little value for an agent selecting the tool.

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 read-only, idempotent query tool, this is complete: it covers when the result matters, what the payload looks like, why repeated rows should not be treated as errors, what aggregated summary is available, and how current the data is. The output schema exists, so return-value structure does not need to be fully repeated here.

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 the parameter documentation already explains `numero_ata`, `unidade_gerenciadora`, `pagina`, and `tamanho_pagina`. The description adds no parameter-specific semantics beyond what the schema already provides, making the baseline 3 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?

The description clearly states the verb and resource: it returns the remaining balance (`saldo`) per ARP item, and even defines `saldo` as 'quantidade ainda disponível'. The resulting concept ('saldo por item') is distinct enough to set it apart from sibling tools such as `compras_arp_itens_listar` and `compras_arp_unidades_item`.

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?

It gives a strong when-to-use signal: the tool is described as critical for adhesion decisions because the ata may be valid but the balance zero. It does not, however, name alternative tools or explicitly say when not to use this one, so it falls short of a 5.

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