Validate local HTML

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

Annotations already establish read-only, idempotent, non-destructive behavior. The description adds valuable context that the file's markup is transmitted to an external third-party service (W3C Nu HTML Checker), which explains the authorization warning. It does not detail response processing, but the output schema likely covers that.

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 two short, front-loaded sentences with no filler. It states the core mechanism first, then the critical authorization constraint, making every word earn its place.

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 single-parameter read-only validation tool with an output schema and strong annotations, the description covers the essential operational facts: input type, external service interaction, and authorization requirement. Nothing critical is missing for an agent to decide whether and how to invoke this tool.

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 provides 100% description coverage for the single filePath parameter, including its type and path semantics. The tool description adds tool-level context about reading local HTML but adds no new parameter-specific meaning beyond what the schema already documents, so the 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 states a specific action ('reads', 'sends its markup to the W3C Nu HTML Checker') and a specific resource ('local HTML file'), which clearly identifies what the tool does. The locally-scoped resource also distinguishes it from the sibling html.url without needing to inspect that 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?

The description clearly frames the tool as operating on local HTML files, and the authorization note ('Use only files the user is authorized to share') provides an important usage condition. It does not explicitly name alternatives such as html.url for remote files, but the local vs. URL distinction is strongly implied by the title and description.

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