measure

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

With no annotations, the description must carry the behavioral burden. It does disclose a key trait: 'without storing it', which signals a privacy-conscious read operation, and 'localhost works' indicates local URL support. However, it omits other behaviors such as whether the URL is fetched live, how long measurement takes, or any rate limits. The disclosure is partial but not contradictory.

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, front-loaded sentence. It leads with the core action ('Measure any URL'), immediately states the privacy trait, and lists the measured aspects in a compact enumeration. Every word contributes to the tool's utility; there is no redundancy or filler.

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 tool's simplicity (one parameter, no output schema, no annotations), the description is largely sufficient. It explains what the tool measures, notes that it does not store the URL, and supports localhost. It could clarify what the agent receives as a result (e.g., a report or scores), but that is not critical for invoking the tool. Overall, it covers the essential context for correct use.

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 coverage is 0%, so the description must explain the parameter. It states the tool measures 'any URL' and explicitly mentions localhost, giving the agent useful context about accepted values. It does not specify protocol requirements (e.g., HTTP/HTTPS) or encoding, but the single parameter is straightforward. The description adds minimal but adequate semantics for the URL parameter.

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 any URL and enumerates specific design aspects (fonts, type scale, spacing grid, palette, contrast, hero, layout). The verb 'measure' is distinct from siblings like search, discover, show, and critique, though it does not explicitly name an alternative. The purpose is specific and unambiguous.

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. It does not mention any exclusion criteria, prerequisites, or situations where another sibling would be more appropriate. The usage is only implied by the action itself, which is insufficient for an agent to make a confident selection.

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