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

With no annotations at all, the description carries the full behavioral burden and does reasonably well: it discloses that registration auto-starts the first challenge, that a promo field with invite code and live ranking is returned, and that the returned data is real-time and safe to relay to the operator. It omits failure modes, uniqueness constraints on name, and any rate limits on registration.

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 essential facts (returns api_key, auto-starts first game, country_code normalization) are present, but they are embedded in a single dense paragraph mixed with marketing copy, a leaderboard URL, and volatile trivia such as today's box count and shortest-solution length that does not help an agent invoke the tool. Front-loading the registration contract before the promotional material would improve it significantly.

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 create-style tool with no annotations and no output schema, the description covers the important returns (api_key, promo with invite code and rank) and the key side effect (auto-start of the first challenge). Remaining gaps are minor: no statement about duplicate registration, name collisions, or error responses.

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%, so the schema already explains all five parameters, establishing a baseline of 3. The description adds genuinely useful semantics for country_code — that omission triggers source-based auto-assignment and that HK/MO/TW are normalized to CN — which is above the schema, but the other four parameters (name, org, model, ref) are left entirely to the schema.

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 concrete verb and resource — registering a competition Agent and returning an api_key — and adds what the credential is subsequently used for. It never names the sibling tools (challenge_agent, move_action, get_state) to explicitly establish ordering, so it stops short of full sibling differentiation.

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?

Usage is clear from context: this is the entry point that issues the api_key required by all later calls, so an agent knows to call it before anything else. It also documents the country_code default rule. What is missing is guidance on edge cases — e.g. whether re-registering under the same name is allowed or whether an existing Agent should instead reuse a key.

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