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

Annotations already declare readOnly, idempotent, non-destructive, and closed-world, so the safety profile is covered. The description adds value beyond that by disclosing the no-cost trait ('Free.') and by naming the content payload — pricing, endpoints, docs — which tells the agent why the call is worth making. It stops short of describing the response shape.

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 sentence with the key qualifier 'Free.' front-loaded, and the content list follows immediately. Every clause carries information, though the sentence is compressed to the point of being slightly telegraphic.

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?

There is no output schema, so the description is the only source of information about the return value, and it says only that there are 'links to docs' and prices without indicating format or structure. For a zero-parameter info tool this is close to sufficient, but the agent cannot predict what it will actually receive back.

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 and the schema is an empty object at 100% coverage with no enums or nesting, so there is nothing for the description to clarify. Baseline 4 applies to zero-parameter tools; no parameter gaps exist.

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 enumerates exactly what the tool returns: what Prescan does, prices of paid tools, HTTP endpoints, and doc links. Combined with the name 'about' and title 'About Prescan (free)', the intent is unmistakable. It lacks an explicit verb, which keeps it from a 5, but it is clearly distinguishable from the action-oriented siblings.

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 leading 'Free.' implies this is the zero-cost discovery call an agent should make before touching paid tools like scan_text or check_x402_endpoint, but that routing is never stated. There are no explicit when-to-use or when-not-to-use instructions, so the agent must infer the sequencing.

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