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

With annotations already supplying the safety profile (readOnlyHint=false, idempotentHint=false, openWorldHint=true, destructiveHint=false), the description still adds real value by naming the return payload (handle, token, cursor 0) in the absence of an output schema. It omits re-join behavior (whether a second join invalidates the previous token) and any auth/error conditions, keeping it out of the 5 band.

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 sentences, zero filler, and the core action is front-loaded before the return-value detail. Every clause carries information.

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 two-param tool with no output schema, the description covers the action, the return shape, and the follow-on call, while annotations cover safety. It lacks only edge-case behavior such as joining a room twice or handling an unresolvable URL.

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% with only two params, so the schema already documents 'handle' and 'room_url'. The description's 'or an alias URL' corroborates the schema's wording but adds no new syntax or format detail; baseline 3 applies.

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 ('Joins') and resource ('a room') plus the accepted input forms (room URL or alias URL), which is enough to separate it from parlor_create and parlor_read. It stops short of naming a sibling or explicitly delimiting scope, so it lands just below the top tier.

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?

There is no explicit when-to-use/when-not guidance or comparison to alternatives, but the note that the returned cursor 0 feeds parlor_read since=0 implies the intended workflow. Usage is inferable rather than stated.

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