crux_history

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

No annotations are present, so the description carries the behavioral disclosure burden. It explicitly labels the operation 'Read-only' and sets expectations about the data window and rolling-period structure. It does not describe ordering or availability caveats, but the output schema is present and the read-only nature is made clear.

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?

Two tight sentences with no filler. The core action and resource are front-loaded, and the secondary detail about the rolling-window format earns its place. 'Read-only' is a concise behavioral flag.

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 read-only history tool with fully described parameters and an output schema, the description covers the important context: resource, time range, and purpose. It could name the direct alternative (crux_field_data) more explicitly, but the one-point-vs-trend distinction already provides adequate orientation.

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?

All 5 parameters have schema descriptions, so coverage is 100%. The description reinforces the origin/URL distinction and the trending purpose, but it does not add significant meaning beyond what the schema already provides for metrics, formFactor, or collectionPeriodCount.

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 states a specific verb and resource: 'Read the Chrome UX Report weekly history for an origin or URL.' It also defines the scope: roughly six months of 28-day rolling windows. It distinguishes the tool from a one-point read by saying it shows a metric 'trending rather than as one point,' which separates it from crux_field_data.

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 description clearly implies the right context: when you need to see a field metric's trend over time rather than a single snapshot. It does not explicitly name an alternative or state exclusions, but the 'rather than as one point' contrast gives an agent a usable selection heuristic.

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