compras_arp_unidades_item

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

Annotations already cover the read-only, idempotent, non-destructive profile. The description adds useful behavioral context by naming the underlying Dados Abertos endpoint and the 15-minute cache, which is meaningful beyond the annotations. It does not contradict annotations.

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 three short sentences with zero filler. The core purpose is front-loaded in the first sentence, followed by the endpoint reference and a brief cache note. Every sentence 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 simple listing tool, the description is complete: it states the resource scope, the endpoint, caching behavior, and the semantic distinction from actual adesões. The output schema exists, annotations cover safety, and the input schema fully documents parameters, so nothing needed for correct invocation is missing.

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?

The description itself does not elaborate on parameters, but schema description coverage is 100%, including the disambiguation note for numero_ata versus numeroControlePncpAta. Per the baseline rule, a fully covered schema makes 3 appropriate even without parameter-specific info in the description.

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 uses a specific verb+resource combination: 'Lista UGs participantes (potenciais caronas) de um item da ARP.' It clearly defines the returned entities as potential carona units, which distinguishes it from the related sibling compras_arp_adesoes_item. The added explanation 'quais unidades podem usar a ata como carona (adesão)' reinforces the precise scope.

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?

The description clearly implies when to use the tool: to determine which UGs are eligible to use an ARP item as carona/adesão. It does not explicitly name alternatives or exclusions, but the phrase 'potenciais caronas' provides enough contextual contrast with actual adesão tools. A direct reference to compras_arp_adesoes_item would make it a 5.

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