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

Annotations declare readOnly, idempotent, openWorld, non-destructive, so safety is covered. The description adds meaningful context: it runs Google's live PageSpeed mobile test, takes 10–40 seconds, returns ranked problems with plain-English fixes, what works, and a shareable report link. This tells the agent the call is slow and external-network-dependent, beyond what annotations state.

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 what it does and the output shape, then usage triggers, then runtime. It is dense but every sentence carries useful information; no filler.

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-only audit tool with no output schema, the description covers purpose, output deliverables, runtime, and usage triggers. Nothing an agent needs in order to call 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%, so the schema documents the url format. The description adds only implied meaning about the URL being a public website address, which is marginal but confirms the resource must be publicly accessible. Baseline 3 would also be defensible, but the 'public website' constraint adds a real semantic requirement not in the schema.

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?

States a specific verb (grades) and resource (public website) with clear scope: scores out of 100 across named categories. The description distinguishes the resource and output shape well enough that an agent knows exactly what the tool produces.

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?

Explicitly says when to use: 'Use when the user asks to audit, grade, check, review or analyse a website, its SEO, speed or conversion.' No alternatives or exclusions are named, and the only sibling is request_help, so a 4 is appropriate.

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