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

With no annotations, the description carries the burden. It does disclose 'Page content is not stored,' which is a useful safety property. However, it does not explain that the tool performs multiple independent checks based on which parameter is supplied, nor does it disclose that most parameters are 'discarded after the check' as the schema indicates. The description adds some behavioral context but misses the multi-purpose nature of the tool.

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 sentence with no fluff. It front-loads the primary function and adds a relevant safety note. Every word earns its place. This is an exemplary model of conciseness.

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 tool has nine parameters, none required, and no output schema. The description covers only the URL behavior, leaving the purpose and interaction of the other eight parameters unexplained. An agent cannot infer when to use this tool for city, feed, json, etc., or what the return format will be. The description is insufficient for a multi-parameter tool of this complexity.

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 every parameter already has a description. The tool description adds meaning to the 'url' parameter by specifying the output (host, scheme, HTTP status), but it provides no extra semantic value for the other eight parameters. Since the schema already documents them, the baseline of 3 is appropriate, with a slight bonus for the URL clarification but not enough to raise the score.

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 verb and resource: 'Return host, scheme, and HTTP status for a URL.' This clearly identifies the core function and distinguishes it from generic tools. However, the tool's schema includes eight additional parameters (city, feed, json, etc.) that are not mentioned in the description, so the stated purpose is incomplete regarding the full scope of the tool.

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?

No guidance is given on when to use this tool versus alternatives like fetch-status, normalize-url, or web-fetch. The description does not mention any exclusions, prerequisites, or conditions that would help an agent decide between this and sibling tools. The only implicit hint is the main purpose, but no explicit routing is provided.

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