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

With no annotations provided, the description carries the full burden of behavioral disclosure. It clarifies the ranking options (popularity vs severity) and implies this is a read operation ('Gets'), but omits critical operational details such as rate limits, data freshness/caching, required permissions, or what constitutes an 'element' in the output.

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 a single, dense sentence that efficiently packs in the resource type (element breakdown), specific metrics (LCP/INP/CLS), and ranking options. No words are wasted, though the lack of a second sentence for usage context or output description slightly limits its utility.

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 15 parameters, no output schema, and no annotations, the description is insufficient. It fails to describe what the output contains (e.g., element selectors, scores, impact values), how pagination behaves with pageSize/pageNumber, or what the 'grouped' parameter does to results. For this complexity level, the single-sentence description leaves significant gaps.

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%, establishing a baseline of 3. The description adds minimal semantic value beyond the schema, essentially summarizing the metricType and rankBy parameters without clarifying syntax details, format constraints, or advanced filtering interactions between the 15 available parameters.

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 retrieves element-level breakdowns for specific Core Web Vitals metrics (LCP, INP, CLS) and mentions ranking criteria. It distinguishes from sibling tools like get_page_performance_breakdown by focusing on specific DOM elements rather than general page metrics, though it could more explicitly contrast with these alternatives.

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 provides no guidance on when to use this tool versus alternatives (e.g., when to use get_page_performance_breakdown instead), no prerequisites (e.g., domain verification requirements), and no warning that it requires a specific pageUrl and metricType to function.

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