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

Annotations already declare readOnlyHint, destructiveHint=false and openWorldHint=false, so safety is covered; the description adds genuinely new context that most callers will get an empty list, which prevents an agent from misreading an empty result as an error. It does not cover ordering, pagination, or the shape of returned faces, but the output schema exists to carry that.

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 short sentences with no padding, and the useful caveat is front-loaded. However, the trailing 'see "note"' fragment is an unfilled template placeholder that reads as broken text and weakens an otherwise tight definition.

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?

With an output schema present and zero parameters, the description only needs to convey scope and the expected-empty behavior, which it does. The unresolved cross-reference to a nonexistent 'note' leaves the agent without the advertised alternative path, so the definition is not fully self-sufficient.

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?

The tool takes zero parameters, so there is nothing for the description to disambiguate; the baseline of 4 applies. The description correctly implies the result set is scoped implicitly by account rather than by any input.

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 names a specific resource ('the photoreal Anam avatars') and a specific scope ('on NodNod's own account that this account may use'), which clearly separates it from the many nod/key/session siblings. The listing verb is only implicit, and the pointer to "note" is a broken cross-reference that muddies rather than sharpens the purpose, so it falls short of a 5.

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 gestures at an alternative ('For an avatar on your own Anam account, see "note"'), which implies a when-not-to-use case, but the reference target is unresolved gibberish — no sibling tool is named, so an agent cannot actually follow the routing. The parenthetical '(most accounts: none yet)' does tell an agent when this tool is relevant, which lifts it above bare minimum.

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