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

With zero annotations provided, the description must carry the full burden of transparency. It details specific operational behavior, such as measuring 'total latency in ms,' retrieving 'key response headers,' and focusing on the lightweight aspect of a 'cheap probe.'

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 entire definition is contained in a single, dense, and highly efficient sentence. It is front-loaded with the action and is structured to maximize information density without becoming verbose.

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 simplicity of the single parameter and the nature of the task, the description provides a complete profile of the tool. It covers scope, output metrics, and intended use case, leaving no critical gaps for the agent.

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 description coverage is 100%, meaning the schema already fully defines the required 'url' parameter. The description simply confirms that the input is a URL, adding no crucial semantic detail beyond what is already covered in the structured input schema.

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 defines the tool's function (Fetch a URL and report) and lists the specific, measurable outputs (HTTP status, latency, headers, page title). This specific list clearly differentiates it from sibling tools like dns_lookup or security_headers.

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?

It explicitly advises on when to use the tool, defining its optimal use case as a 'cheap liveness/uptime probe.' This provides necessary context for choosing it over more comprehensive or slower tools.

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