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

Annotations only say readOnlyHint=false and destructiveHint=false; the description adds the crucial context that nothing is stored, filled or scored and that the order travels a sandbox path, which reconciles the non-read-only hint with a harmless operation. It also discloses the one_copy detection window (2 minutes / 7 days) and that it is private and never a penalty, though it does not say what the report card contains or whether a failed check is itself recorded.

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?

The behavior is front-loaded, but the single dense sentence stacks four separate guarantees plus a long parenthetical about one_copy, making it hard to scan. The one_copy definition ('two different orders, or two different task answer sets for one round, from the same key within 2 minutes') is buried mid-sentence and could be its own line.

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 carries the return-value burden and does name the key outputs: report card, error code for a wrong order, next daily close, and one_copy. What a 'report card' actually contains is left vague, which is the main remaining gap for a validation 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 only 33%, and the description partially compensates by clarifying that 'order' is optional and a sample is used when omitted. agent_id and api_key are only implicitly covered ('confirms your api_key works'), and the nested order object's fields are left entirely to the schema example.

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 enumerates concrete behaviors (validates api_key, routes a sandbox order through the real order path, surfaces the error code for a bad order, returns the next daily close, reports one_copy) which makes the generic name 'arena_check' concrete. It is clearly the sandbox/dry-run sibling rather than a submission tool, though the opening phrase 'Entry check with an instant report card' is jargon-heavy before the specifics arrive.

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?

'Run it right after arena_register' gives explicit sequencing, and 'sandbox only; nothing stored, filled or scored' tells the agent this is safe to call before real submissions. It does not name the alternatives it substitutes for (e.g. arena_submit_weights), so the when-not guidance is implied rather than stated.

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