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

Annotations already declare readOnlyHint=true, openWorldHint=false, and destructiveHint=false, so the safety profile is covered. The description adds that it reflects 'right now' state, which is useful for a live session. However, since an output schema exists, restating the returned fields (state, joiners, scores) adds little behavioral value, and no error or freshness guarantees are disclosed.

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 tight sentences, front-loaded with the core purpose before the example questions. The embedded example questions are mildly verbose but directly aid selection and earn their 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?

With annotations covering safety and an output schema describing return values, the description needn't re-explain results; it complements them with a 'live/right now' framing. It omits failure handling (invalid or expired room code), which is a minor gap for a single-param read tool.

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% and the single room_code parameter is thoroughly documented (length, case-insensitivity, excluded characters, example). The description adds nothing about the parameter, so the schema does the heavy lifting — baseline 3.

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+resource ('Check what is happening in a Fun Friday session') and enumerates the returned facets: lobby/play state, participants, and scores. This clearly separates it from siblings like funfriday_list_sessions (enumerate sessions) and funfriday_get_leaderboard (rankings).

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?

Provides concrete triggering questions ('has everyone joined yet?', 'who is winning?') and a context cue ('without opening the browser'), which tells the agent when to reach for this tool. It stops short of naming alternatives or stating when not to use it (e.g., vs funfriday_list_sessions).

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