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

Annotations already declare readOnlyHint=false and destructiveHint=true, so mutation is known; the description adds genuinely new context — that a real, immediately joinable room is created and that it consumes one of the team's games for the week, which implies a quota. The user-confirmation requirement is a behavioral constraint not derivable from the annotations.

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, front-loaded with the action and its payoff (room code and join link), followed by the side effect and the confirmation guardrail. No filler or restated name/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 annotations covering the safety profile and an output schema covering return values, the description supplies the missing operational context: real-world room creation, weekly game consumption, and user confirmation. It does not address whether starting a session conflicts with or supersedes an already-active one, a minor gap for a create 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 game_type property already documents the enum, the display-name mapping (Imposter="faker"), and the pointer to funfriday_list_games. The description adds only the indirect hint that the chosen game draws on the team's weekly allotment, 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?

States a specific verb and resource ("Start a new Fun Friday game session") and immediately distinguishes itself from the sibling read tools by noting it returns a room code and join link. An agent can tell it apart from funfriday_get_session and funfriday_list_sessions without opening any schema.

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 a clear precondition ("confirm with the user before calling it") and the schema points to funfriday_list_games when the game key is unknown. It stops short of explicit when-not guidance or naming which sibling to use instead when a session already exists.

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