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

The readOnlyHint=false annotation already signals this is a write; the description adds the useful behavioral fact that the call is required at first login. However, it says nothing about what gets created, whether the appearance can be changed afterwards, or what happens on a repeat call, which is the main unknown for a one-time setup mutation.

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?

One purpose sentence with the timing constraint up front, then a terse semicolon-delimited parameter legend. No filler, and the highest-value constraint (mandatory at first login) is front-loaded.

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 7-parameter, 6-required mutation with no output schema and only a readOnlyHint annotation, the description covers purpose, timing, and every numeric domain. The remaining gaps — post-call state and re-invocation behavior — are real but secondary for a character-creation step.

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 0%, so the description carries the entire burden — and it delivers concrete value ranges for type, body, bust, head, skin, and hair, including conditional rules (male type 1 → body 1..5, female-only bust, female type 3 → head 1..5). The `male` boolean is covered only implicitly through the gendered wording, but the compensation over an empty schema is substantial.

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?

"Выбрать внешность нового персонажа" names a specific verb (choose/set) and a specific resource (appearance of a new character), and the parenthetical "обязательно на первом входе" pins down the exact moment it applies. An agent can distinguish it from game_register or game_genetic on purpose alone.

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?

It states clearly when the tool must be used: mandatorily on the character's first entry, which is actionable timing guidance. It does not name an alternative or say what happens if the agent skips it, so it falls short of a 5.

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