get_crux_history

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

With no annotations, the description carries the full behavioral burden. It does disclose useful behavior — 28-day window, 25+ weekly collection periods, the exact metric set returned, and the API-key fallback chain (GOOGLE_API_KEY / CRUX_API_KEY) — but says nothing about quotas, rate limits, error/empty-data behavior, or when history is unavailable for a low-traffic origin.

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?

Front-loaded with the API and scope in the first sentence, followed by the return shape, then a compact Args block. No filler, though the Args list slightly restates parameter names already visible in the schema.

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?

An output schema exists, so return values need not be described, and both parameters are covered including the auth fallback. The remaining gap is deciding between this and get_crux_metrics plus operational caveats like rate limits or missing-data cases.

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 description coverage is 0%, so the description must compensate, and it largely does: it explains url_or_origin accepts either a full page URL or an origin domain with an example, and clarifies that api_key is optional by describing the environment-variable fallback. It stops short of format/filtering details for url_or_origin (e.g., protocol requirements).

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 (Query) and resource (Chrome UX Report History API) and scopes it to 28-day historical field metric trends with named metrics (LCP, INP, CLS, FCP, TTFB). This implicitly separates it from the get_crux_metrics sibling, but it never explicitly contrasts the two, so an agent must infer which one returns snapshots vs. history.

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: 'historical field metric trends' suggests reaching for this when a timeseries is wanted rather than a single snapshot, but there is no explicit when-to-use, when-not-to-use, or named alternative (get_crux_metrics) to route between them. No prerequisites (e.g., that a URL/origin must have sufficient CrUX traffic) are given.

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