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

Beyond the single readOnlyHint=false annotation, the description discloses two non-obvious behavioral traits: the target player must confirm, and while the challenge is unresolved, world movement steps are blocked. That side effect is exactly the kind of context annotations cannot convey. It stops short of describing failure modes, cooldowns, or what the caller receives.

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?

One compact sentence with the action front-loaded and the prerequisites in a parenthetical. Every clause carries information; nothing is redundant. Slightly dense punctuation, but appropriate for the amount of constraint conveyed.

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 mutating one-parameter tool with no output schema and only a readOnlyHint annotation, the description covers timing, location, and blocking behavior well. The remaining hole is the parameter's meaning and validity conditions, which an agent needs to call it correctly.

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 0% for the single required parameter 'login', so the description carries the full burden. It never identifies 'login' as the opponent's login or constrains it (e.g., must exist, must be online, must be co-located). The phrase 'Вызвать игрока' implies a target but leaves the parameter's identity and validity rules to inference.

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 states a specific verb and resource in Russian ('Вызвать игрока на дуэль с подтверждением'), which is clearly a challenge action distinct from the sibling game_duel_answer and game_duel_cancel. It does not explicitly name those siblings as alternatives, but the action itself is unambiguous.

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?

Strong preconditions are given: call only after game_player_info, no sooner than one second later, and only when both players are on the same cell outside the Ocean dome. What is missing is guidance on when to prefer this over related duel tools or what to do if the challenge is declined, but the when-to-use conditions are unusually explicit.

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