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

Annotations cover mutation/safety hints (readOnlyHint=false, destructiveHint=false, idempotentHint=false), so the bar is lower. The description adds genuinely non-structured behavior: multiplayer/solo consume paid x402 ranked access while sample is free and unranked. It stops short of describing cost magnitude, failure behavior, or what the start call returns.

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 tight sentences with no filler, and the core capability statement is front-loaded before the mode economics and sibling routing. Every clause carries information an agent needs.

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 start-action tool with no output schema, the definition covers capability, mode constraints, and lifecycle routing. The remaining gap is that it does not say what a successful start yields (e.g. a game handle needed for manage_game), but annotations and siblings carry most of the rest.

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%, so the schema already documents all five parameters, including mode semantics and the sample-eligible game list. The description largely restates the mode/game constraints already present in the enum descriptions, adding only marginal framing.

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 precise verb and resource ('Start game activity only') and explicitly demarcates itself from the two siblings that handle the other lifecycle stages (manage_game for continue, get_game for inspect). An agent can place this tool in the flow without reading 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 explicit routing: continue with manage_game, inspect with get_game. It also specifies when each mode applies (multiplayer/solo use paid x402 ranked access; sample is free/unranked and restricted to four games), which is exactly the when-to-use guidance needed to choose a mode.

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