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

No annotations, so the description carries the full burden. It usefully discloses the return payload shape (lab vs field metrics, plus history), but says nothing about whether it triggers a fresh measurement or returns cached results, how stale the 'latest' score may be, or any rate/latency constraints — meaningful gaps given the sibling scan_site implies live runs are a separate operation.

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 enumerates the return contents without filler or repetition. Every clause earns its place by telling the agent what data comes back.

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 one required parameter, no output schema, and no annotations, the description does most of the needed work by describing the return payload in detail. The main remaining hole is operational behavior — cached vs live, and freshness guarantees — which an agent would want before invoking it.

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?

Single parameter with 100% schema description coverage that already points at list_sites for obtaining site_id. The description adds no further semantics about the identifier or any accepted scope, so baseline 3 applies.

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 resource (PageSpeed data for a site) and enumerates exactly what it returns: Lighthouse score, lab metrics (LCP/CLS/TBT/FCP), field/CrUX data, and score history. It is clear enough to distinguish from retrieval siblings like get_site or get_findings, though it never names an alternative 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?

Usage is only implied — the name and the 'latest score' phrasing suggest a read of current performance data, and the schema ties site_id to list_sites. There is no statement of when to prefer this over scan_site or probe, nor any prerequisite such as an existing scan before data is available.

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