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

Annotations already cover the safety profile (readOnlyHint=true, destructiveHint=false, openWorldHint=false), so the bar is lower. The description adds genuinely useful behavior beyond them: this is a live 'right now' snapshot and the session has distinct lobby vs. playing states, implying the result changes over time and between calls.

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 payload contents are front-loaded before the example use cases. Every clause earns its place.

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 single-parameter read tool with a full input schema, an output schema, and annotations covering safety, nothing material is missing. The description supplies the liveness framing that the structured fields cannot express.

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?

There is one parameter and schema coverage is 100%, so the schema already documents room_code fully, including its six-character format, case-insensitivity, and excluded characters. The description adds nothing about the parameter, which is the expected baseline when the schema does the work.

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 and resource ('check what is happening in a Fun Friday session') and enumerates the payload: lobby/playing status, joined players, current scores. It is clear, but it does not distinguish itself from the sibling funfriday_get_leaderboard, which the phrase 'who is winning?' could equally point to.

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?

Gives concrete triggering questions ('has everyone joined yet?', 'who is winning?') and a framing condition ('without opening the browser'), which tells the agent when this is the right call. It stops short of naming an alternative tool or a when-not condition, so it lands at clear-context rather than explicit routing.

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