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

With no annotations, the description carries the full burden, and it does disclose the payload contents (open rooms plus in-progress wars), which is the key behavior for a listing tool. However, it says nothing about read-only safety, auth requirements, result size, or pagination, leaving meaningful behavioral gaps.

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?

A single front-loaded sentence with no filler; it efficiently states the two result categories. The sentence fragment style is terse but not wasteful.

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?

With no output schema, the description must stand in for return-value documentation; it names the two result categories but does not describe their shape, ordering, or volume. For a zero-param read tool this is adequate but thin.

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 tool takes zero parameters, so the baseline is 4; there are no inputs whose semantics need explaining.

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 names the two resources it surfaces — rooms awaiting players that are joinable by code, and wars in progress — which is more specific than a bare name restatement. The verb ('list/open') is implicit rather than stated, but an agent can tell this is a discovery tool distinct from recent_wars or join_war.

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: the phrase 'that you can join by code' hints this is a pre-join discovery step, but there is no explicit when-to-use, no mention of join_war or recent_wars as alternatives, and no stated prerequisites.

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