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

Annotations already declare readOnlyHint=true and openWorldHint=false, and the description adds real behavioral context beyond them: the widget runs client-side ('measures the visitor's photo in their browser'), requires 'no sign-up', and embeds a mandatory visible credit link. Those details affect how an agent presents and explains the snippet. It stops short of 5 since nothing about permissions, rate limits, or delivery format is stated.

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?

A single front-loaded sentence that leads with the artifact before the parenthetical clarifications; nothing is redundant. The nested parentheses make it slightly dense but no sentence is wasted.

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 no output schema, the description carries the return-value burden and does describe what the snippet contains (embed HTML plus a visible credit link). The only untouched element is the 'size' parameter, which the schema fully covers, so an agent has nearly everything needed to call and explain this tool.

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 100% and the single enum parameter 'size' already documents its three values with pixel widths. The description never mentions size, so it adds nothing beyond the schema, making the baseline 3 correct.

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 precisely names the artifact returned (pasteable HTML for the face shape finder) and its function, which is distinct from every sibling (citations, face-type lookups, statistics). The verb is implicit rather than stated ('get'/'return'), so it falls just short of the crisp verb+resource pattern.

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 implies the audience and use case ('a website owner can paste to add the free face shape finder'), which signals when this tool is relevant. However, it gives no explicit when-to-use vs alternatives guidance or exclusions relative to siblings like get_citation or get_methodology.

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