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

Annotations already declare readOnlyHint, idempotentHint and destructiveHint=false, so safety is covered. The description adds a genuinely useful behavioural fact not in the annotations: it requires an authenticated Mizan session. It also hints at the shape of the result (per-community role, registry status, game servers), which the output schema presumably formalises.

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?

Two short sentences, front-loaded with the action and scope, followed by the authentication precondition. Every clause carries information and nothing is repeated from the title.

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 parameters, an output schema present and annotations covering the safety profile, the description supplies exactly the missing pieces: the authentication requirement and a summary of what is returned. Nothing needed to invoke the tool correctly is absent.

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 there is nothing for the description to disambiguate. Baseline 4 applies; the description correctly avoids inventing filtering options that do not exist.

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?

States a specific verb ('List') and scoped resource ('the communities you belong to on Mizan'), and further specifies what the response contains (role, registry status, game servers). This clearly distinguishes it from siblings: registry_stats reports aggregates, list_sources and lookup_player are unrelated, and check_players targets players rather than the caller's memberships.

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 phrase 'you belong to' and the sign-in requirement make the context of use clear: this is the caller's own membership view, available only when authenticated. There are no explicit when-not conditions or named alternatives, but no sibling overlaps enough to need one.

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