web_vitals

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

Discloses that it injects Google's official web-vitals library from CDN, listens for each metric, and returns after all expected metrics fire or timeout. This is transparent for a read-like operation; no annotations exist to contradict.

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 short sentences: purpose, mechanism, best practice. Every sentence adds value with no redundancy.

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 tool's complexity (5 metrics, library injection) and presence of an output schema, the description adequately covers usage and behavior. Could mention output format briefly, but output schema likely handles that.

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?

The schema has 0% description coverage. The description mentions 'returns after all expected metrics fire or timeout elapses', clarifying the timeout parameter's role. This adds some value but could be more explicit about units or range.

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 it collects Core Web Vitals (LCP, CLS, INP, FCP, TTFB) via web-vitals v4, injecting a library and listening for metrics. This is specific and distinguishes it from sibling tools like performance_metrics which are more general.

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?

Provides a best practice: call after page interaction for INP and CLS signal. This guides usage context, but does not explicitly state when not to use or suggest alternatives.

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