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

Annotations already flag destructive/non-idempotent/write, and the description adds genuinely new context: the gain/loss leaves the standings, the reset is recorded beside the name, nothing real is affected, and it costs 2 units. It also discloses the required confirmation and key.

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?

Front-loads the core action then uses labeled segments (Returns/Behavior/Errors) that make scanning easy. The Behavior sentence is dense and slightly convoluted, but every clause carries 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?

With no output schema the description still explains the return (the account as arena_state), the cost, the side effects, and the error modes. An agent has everything needed to call and interpret it.

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 schema already documents 'sure' must be true. The description reinforces this by describing the error when it is absent, adding meaning beyond the raw type, though it adds no new syntax detail.

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 compound action: closes every open position and resets the account to $1000. It explicitly distinguishes itself from arena_close (single position) so an agent can route correctly without opening either 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 an explicit when-to-use ('Use only to start over') and names the alternative ('to close one position use arena_close'), plus the failure conditions ('refused without sure set to true, or without a key'). Nothing is left to inference.

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