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

Annotations already establish this is a read-only, non-destructive, non-open-world operation, so the bar is lower. The description still adds value by disclosing the actual validation dimensions (duplicates, date/protocol errors), which tells the agent what a run will surface beyond the generic safety hints.

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?

One sentence, front-loaded with the action and resource, then the concrete checks. Every clause earns its place with no padding.

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 one-parameter, read-only validation tool with annotations and no output schema, the description covers what the agent needs to call it correctly and what kinds of findings to expect. Only the precise response shape is left unspecified, which is a minor gap given no output schema exists.

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?

There is a single 'xml' parameter with full schema description coverage, so the schema already documents it. The description only marginally adds meaning by clarifying it may be a sitemap or sitemap index; baseline 3 is appropriate when the schema does the work.

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?

States a specific verb (validate) and resource (XML sitemap/sitemap index) and enumerates exactly what is checked: URL count, duplicates, invalid URLs and dates, protocol errors. This clearly separates it from siblings like validate_schema or analyze_robots_txt, which target different artifacts.

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 phrase 'you pass in' usefully signals the caller supplies XML content rather than a URL to fetch, which is real usage context. However, there is no explicit when-to-use/when-not guidance and no routing to or away from sibling tools.

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