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

The description discloses important side effects: completed results stay, the change is shown in a specific format, and unknown substitute names are added to the roster automatically. This goes well beyond the sparse annotations (readOnlyHint false, destructiveHint false) and helps the agent anticipate consequences.

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 sentences, front-loaded with the core action, then two situational details. No filler or repetition of schema content. Every sentence carries meaningful information.

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?

The description covers the two distinct phases, mode selection, result retention, and auto-add behavior. Since an output schema exists, return values are not needed. Minor gaps: no mention of permissions or idempotency, but request_id is documented in the schema and idempotency behavior is implied there.

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?

With schema coverage at 40%, the description compensates by explaining the mode enum values (slot_swap default vs regenerate), the role of levels in regenerate mode, and the auto-add behavior for names. It doesn't elaborate on out_player_name or request_id, but those are self-explanatory from their schema descriptions.

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 action: a substitute takes over a player's spot, with two modes (slot_swap and regenerate). This clearly distinguishes it from sibling tools like remove_player or withdraw_player, which have different semantics.

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?

The description provides explicit usage context: during play vs before the first result, and explains which mode to choose in each situation. It also notes auto-add behavior for unknown substitutes. It doesn't explicitly name alternative tools, but the situational guidance is clear.

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