CrUX: current Core Web Vitals

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

Annotations already cover read-only, idempotent, and non-destructive behavior. The description adds useful context about the return format (p75 with assessments, core_web_vitals_pass) and the raw=true option, which are not stated in the schema. No contradictions found.

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?

The description is two compact paragraphs with a clear opening statement followed by necessary parameter and output details. Every sentence adds value, with no filler or repetition, and it is appropriately front-loaded.

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?

Given the 4 optional parameters and existing output schema, the description covers all key aspects: how to specify origin vs url, form_factor options, raw flag, and what the response contains. It is sufficient for correct invocation without additional external documentation.

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?

With 0% schema description coverage, the description fully compensates by explaining all four parameters: origin/url mutual exclusivity, form_factor allowed values, and raw behavior. It adds meaning beyond the schema's type/default details.

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 clearly states the tool returns 'Current p75 Core Web Vitals for an origin or a single URL' with a specific resource (CrUX data) and scope (origin or URL). It distinguishes itself from siblings via 'current' and explicit mention of the metrics and pass/fail assessment.

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 gives clear guidance on parameter usage ('Pass EITHER origin OR url') and form_factor values, but does not explicitly mention when to use this tool versus alternatives like crux_history or crux_compare. Usage context is implied ('current') but not contrasted with siblings.

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