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

Annotations only signal non-readOnly/non-destructive; the description adds real behavioral detail: display text is sanitized, reserved names are refused, and the presence is publicly rendered. This goes beyond the annotation booleans and contains no contradiction.

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 sentences with no filler: the action and parameters come first, then the public context, then constraints and auth. Every sentence earns its place.

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 4-parameter tool with no output schema, the description covers purpose, side effects, constraints, auth, and public visibility. It does not describe the response shape, but that is less critical given the enum-constrained inputs and no output schema.

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 only 50%, so the description compensates by enumerating sprite and mood options and adding constraints not in the schema (sanitization, reserved-name rejection). It does not deeply elaborate every parameter, but the enums are self-explanatory and the added constraints are meaningful.

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+object: 'Register (or refresh) this account's presence in the playground world,' and gives the public stage URL. This makes it distinct from sibling playground tools like playground_state (viewing state) and playground_act (taking action).

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 clear context for when to call: to set or refresh a live presence on the public stage, and it states the auth prerequisite. It does not explicitly name an alternative or a when-not condition, so it stops 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.