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

Annotations already declare this is a non-read-only, non-destructive, non-open-world action, so the bar is lower. The description still adds real behavior: free listings install automatically, paid listings hand off to the Ania site, which tells the agent the call can end in an external checkout flow rather than an install. It does not say whether the previous avatar is replaced or retained, but the added context is substantive.

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, zero filler, and the core action is front-loaded before the free/paid consequence. Every clause carries information the agent can act on.

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 single-parameter mutation with no output schema, the description covers the action, the required input, and the two distinct outcomes. Minor gaps remain (reversibility, what happens to the current avatar, what a paid handoff returns), but nothing essential to invoking it correctly is missing.

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% and the single parameter already carries 'Marketplace listing id', so the description's 'Takes a listing id' adds almost nothing beyond that. Baseline 3 applies because the schema does the work for this one-parameter tool.

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 pairs a specific verb ('Switch') with a specific resource ('the connected player to another avatar from the marketplace'), which is enough to distinguish it from get_avatar, create_avatar, and cancel_avatar. It stops short of naming a sibling to route against, so it is clear but not maximally differentiated.

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 implies when to use it (you have a marketplace listing id and want to change the active avatar) but never states preconditions, alternatives, or exclusions. The free-versus-paid split is useful context, though it describes outcome rather than telling the agent when to prefer this tool over open_in_player or install_in_project.

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