seo_core_web_vitals

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

With no annotations provided, the description carries the behavioral burden. It honestly says 'Estimate' rather than 'measure', indicating the results are approximations based on HTML analysis, and it enumerates specific detectable issue categories. This gives useful behavioral expectations without overpromising real-world lab or field data.

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 compact and front-loaded: the core purpose and metrics appear in the first sentence, followed by a tight bulleted list of issues. Every sentence earns its place, and the structure makes the tool's capabilities easy to scan.

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?

The description adequately covers what the tool does, its input basis, and the categories of findings it produces. There is no output schema, so some return-format detail is missing, but for a two-input analysis tool the provided description is otherwise sufficient for an agent to invoke it correctly.

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 100%, so both parameters (url and html) are already documented in the schema. The description adds the useful context that analysis is performed 'from HTML', but it does not further clarify the role of the URL parameter beyond what the schema says. A baseline 3 is appropriate.

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 action ('Estimate') with a clear resource (Core Web Vitals) and the concrete metrics involved (LCP, CLS, INP, TTFB). It also lists the types of issues detected, making the tool's role clear and distinct from the sibling SEO tools.

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 when to use this tool: when the user has HTML content and wants Core Web Vitals estimates or HTML-related performance issue detection. It does not explicitly name alternatives or exclusions, but the scope is specific enough that an agent can select it confidently among the SEO sibling tools.

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