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

Annotations already declare the tool as read-only (readOnlyHint=true), idempotent, and non-destructive. The description adds no extra behavioral context beyond confirming it's about group composition, which aligns with the annotations. It doesn't discuss side effects, authorization, or other details, but for a read-only query tool, the annotations cover the essential safety profile.

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 two concise sentences in Portuguese, immediately stating the purpose and providing a relevant example. Every word contributes to understanding, and it's appropriately front-loaded with the main function.

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?

Given the simple nature of the tool (one optional parameter, read-only), the description covers the core functionality and return content (teams and games per group). However, the lack of parameter documentation is a significant gap, as the agent cannot know how to specify a group. The example hints at using a country name but doesn't define the exact format or allowed values.

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 single parameter 'group' (type string) is not mentioned in the description at all. Schema description coverage is 0%, and since there are no enums or examples, the agent has no guidance on what values to pass (e.g., 'A', 'B', 'Brasil'). The description fails to compensate for the sparse schema, leaving the parameter entirely undocumented.

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 it provides the composition of groups (12 groups of 4 teams) with teams and games. It also includes a concrete use case ('quem está no grupo do Brasil'), making it specific to group queries and distinct from sibling tools like worldcup_matches or worldcup_bracket.

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 gives a clear usage example ('Use para quem está no grupo do Brasil') that tells the agent when to call this tool. It doesn't mention when not to use it or name alternatives, but the context inferred from the example is sufficient for a simple tool.

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