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

The annotations already declare readOnly, idempotent and non-destructive, so the safety profile is covered. The description adds genuinely new behavioral context: the immutability guarantee ('cannot change policy') and the inheritance rule that a room choice applies to every channel in that room, which an agent could not infer from the structured fields alone.

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?

Three short sentences, front-loaded with the core action and followed by the two constraints that matter. Every sentence carries distinct information with no filler.

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 read-only getter with full schema coverage and no output schema, the description covers action, scope and immutability. It does not hint at the shape of the returned sharing choice, which is the only remaining gap given there is no output schema to describe it.

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 coverage is 100%, so both room_id and connection are fully documented in the schema, including the '*' convention. The description's '*' note largely restates the schema rather than adding syntax or format detail, so the 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?

The description delivers a specific verb+resource ('Read this agent's current message-sharing choice for a room') and explicitly carves out what it is not ('This tool cannot change policy'), which functionally separates it from the sibling sharing_setting_request. The '*' semantics and the room-vs-channel scope rule further pin down exactly what is being read.

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?

It gives a clear usage rule ('Room ID \'*\' reads the default') and an implicit exclusion, since it states the tool cannot change policy, steering policy changes to the sibling sharing_setting_request. It stops just short of naming that alternative explicitly, so it is clear context rather than full when/when-not guidance.

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