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

Annotations already declare destructiveHint=true and idempotentHint=true, so the safety profile is covered structurally. The description still adds real value beyond them: the preset exclusion, the fact that past session records are retained, and the api_key requirement with its provenance.

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 compact clauses, front-loaded with the core action and each carrying distinct information (scope restriction, data retention, auth need). No filler or restatement of the name.

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 destructive mutation with no output schema, the description covers the important gaps: what is destroyed, what survives, and what auth is needed. Only the avatar_id parameter's semantics remain unaddressed.

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 50%: api_key is described but avatar_id is bare. The description enriches api_key by naming its source (admin panel-issued key), but adds nothing on avatar_id's format or origin, so it only partially compensates for the uncovered parameter.

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?

Names a specific verb and resource ('自分で作ったアバターを消します') and immediately scopes it with a constraint ('プリセットは消せません'), clearly distinguishing it from sibling write tools like create_avatar and read tools like list_avatars/get_avatar.

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?

Provides a clear when-not condition (presets cannot be deleted) and states the authentication prerequisite (api_key issued via admin panel). It doesn't explicitly point to an alternative for finding a valid avatar_id, but the usage context is easy to infer.

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