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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false, and openWorldHint=false. The description adds useful behavioral context beyond annotations by stating that an api_key is required and that the key is issued from the admin panel.

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 description is front-loaded with the purpose, then adds the key usage detail and authentication requirement. Every sentence is short and earns its place with no redundancy.

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 simple list tool with rich read-only annotations and complete one-parameter schema coverage, the description covers scope, downstream id usage, and authentication. No output schema exists, so return-value details are not required.

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 api_key is already documented as a string with the sk_live_ prefix. The description adds useful meaning by clarifying that the key is required and is issued in the admin panel, going beyond the schema's format-only note.

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: it returns usable avatars, explicitly scoping them to presets and ready avatars created in this tenant. This distinguishes it from siblings like get_avatar, create_avatar, and delete_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?

The description gives clear downstream usage: use the returned id for create_session's avatar_id. It implies the context for selecting an avatar before creating a session, but it does not explicitly name alternatives such as get_avatar or state when not to use this tool.

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