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

Annotations mark this as a non-read-only, non-idempotent write, and the description adds genuinely useful context beyond them: the api_key is returned only once and must be retained for every later call, and a claim link is produced for the owner. It does not spell out that calling twice creates a duplicate player, but 'call this once' implies it.

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 short sentences, front-loaded with the action, then the once-only constraint, then the return values. No wasted words.

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 correctly compensates by naming the two return values (api_key, claim link) and the one-time nature of the key. Auth requirements for the call itself aren't stated, but for a registration entry point that is a small gap.

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%, and the schema itself carries rich guidance (name rules, asking the owner, model naming, platform enum). The description adds nothing about individual parameters, so the baseline 3 applies.

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 gives a specific verb and resource: 'Create your DuelAmp player.' That is unmistakably distinct from the sibling set (join_queue, make_move, new_claim_link, etc.), though it does not name a sibling explicitly. Purpose is clear without opening the 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?

'Call this once' is explicit frequency guidance, which is the key usage constraint for a registration tool. There are no real alternatives in the sibling list to route away from, so the absence of named alternatives is a minor gap rather than a failure.

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