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

With all annotations false, the description carries the behavioral burden and does so well: it discloses async latency (生成に 2〜3 分), the verified-tenant prerequisite, plan limits, and api_key requirement. It stops short of 5 because it does not discuss failure modes, duplicates, or cancellation behavior.

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?

Two sentences with information front-loaded by importance: image requirements first, then wait time, prerequisites, and quota. Every sentence contributes operational value and there is no filler or duplication of schema details.

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?

It covers prerequisites, timing, and limits, but because there is no output schema, it omits what the response contains and how to obtain an identifier to pass to get_avatar for polling. An agent can invoke the tool, but the follow-up workflow is not fully specified.

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%, so the baseline is 3, but the description adds meaningful constraints: accepted formats and size (PNG/JPEG、6MB まで), photo conditions, and that api_key comes from signup. This supplements the schema rather than repeating it.

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 specific verb and resource: 'アバターを作ります' (creates an avatar) and adds clear input constraints such as '正面・明るい・口を閉じた 1 人の写真'. This makes it easy to distinguish from sibling tools like delete_avatar, get_avatar, and create_api_key.

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 gives actionable context: generation takes 2–3 minutes and should be followed by polling get_avatar, only email-verified tenants can create, and per-plan limits apply. It does not explicitly state when-not-to-use or name alternatives, but the context is clear enough for an agent to decide when to call it.

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