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

The description claims to 'measure' page load performance, implying a read operation, but annotations set destructiveHint=true, which contradicts the read-only nature. The description does not explain potential side effects (e.g., making an HTTP request to the target URL) nor the cost mechanism beyond a brief mention. This contradiction undermines trust.

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 sentences: first defines action and result, second details return values, third lists use cases and cost. No wasted words, logically structured, and front-loaded with the core purpose.

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?

For a simple measurement tool with two parameters and no output schema, the description covers the core functionality, return values, use cases, and cost. Lacks details on prerequisites, error handling, or rate limits, but is largely sufficient for typical usage.

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 input schema already provides 100% coverage with clear descriptions for both parameters (url and origin). The description adds no additional parameter-level information, sticking to describing the return value. Baseline score of 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 clearly states the tool measures real-world page load performance (response time) for any URL from a chosen global location. The verb 'measure' and resource 'page load performance' are specific, and the tool is easily distinguished from its siblings which focus on addresses, business info, weather, etc.

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 notes usefulness for global latency monitoring, CDN validation, and uptime/performance checks. It does not explicitly state when not to use or compare to alternatives, but given the sibling tools are entirely different domains, the usage context is clear. Mentioning cost provides some practical guidance.

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