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

The readOnlyHint annotation already declares this is a non-mutating read, so the bar is lower. The description adds useful return context by saying the response includes details plus a preview image, which the annotations do not convey. It says nothing about error behavior for unknown ids or whether the preview is a URL or embedded data.

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?

One short sentence with zero filler, and the key noun (preview image) is front-loaded alongside the resource. It is efficient, though its brevity borders on under-specification rather than tightness.

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 one-parameter read tool with no output schema, the description covers the essential shape of the return (details plus preview image) and the singular scope. However, the undefined identifier semantics leave a genuine gap an agent must guess at. No annotations beyond readOnlyHint need supplementing.

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 description coverage is 0% for the single required 'id' parameter, so the description carries the full burden and does not meet it. It never clarifies whether 'id' is a mascot identifier, a slug, or a name, nor what format is expected. 'One mascot' hints that the argument selects a single entity, but adds no real semantic detail.

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 and scope: 'Details and a preview image of one mascot,' which distinguishes it from the plural listing sibling list_mascots by emphasizing a single mascot. The verb is implicit ('details ... of one mascot') rather than an explicit 'retrieve', but an agent can still infer the operation. It stops short of naming any sibling explicitly.

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?

There is no guidance on when to call this versus list_mascots, edit_mascot, or the other mascot-related siblings. No prerequisites or exclusions are stated; the agent must infer that this is the read path for a known mascot id.

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