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

Annotations already declare readOnlyHint=false, idempotentHint=true, destructiveHint=false and openWorldHint=true; the description adds real value beyond that by explaining the side effect ('Goppa reads the site's home page'), the non-effect ('nothing on the site changes'), and a quota consequence ('counts toward the sites your account includes'). It does not mention what happens if the account's site limit is reached.

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, front-loaded with purpose and then side effects, all substantive. Minor redundancy between 'nothing on the site changes' and 'changes nothing' in the final sentence, but the quota note 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?

With an output schema present, return-value explanation is unnecessary, and the description covers the mutation's effects, its external read behavior, and idempotency. The remaining gap is failure/quota-exceeded behavior, which is not described.

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?

There is a single parameter with 100% schema description coverage, so the baseline is 3. The description adds no format guidance (no scheme/protocol rules, no subdomain or path handling) beyond the schema's 'like yourstore.com' example.

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 opens with a specific verb+resource ('Add one of your websites to your Goppa account') and states the resulting benefit ('check, measure and track it'). It is unmistakably the only write/creation tool among a list of read-oriented siblings, so no disambiguation is needed.

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 clarifies the intent — registering a site so Goppa can monitor it — which is adequate context for choosing this tool. It also notes the idempotent case ('adding a site that is already in the account changes nothing'), but never states prerequisites, limits, or what to do if the site is already tracked instead.

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