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

Annotations cover the safety profile (readOnlyHint=false, destructiveHint=false, non-idempotent), so the bar is lower, yet the description adds substantial behavior: confirm=false previews vs confirm=true creates, the DNS/nameserver handoff, the explicit warning never to hand out CNAME/A records, and the no-extra-cost hosting model.

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?

Front-loaded with the core purpose and tightly written across several dense sentences; the DNS and follow-on guidance earn their place. Slightly long, with some explanatory copy ('at no extra cost') that borders on persuasive rather than operational.

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 mutating, open-world tool this is thorough: creation flow, preview vs commit, DNS responsibility, edge case, and downstream tool routing are all covered. An output schema exists, so return-value explanation is legitimately omitted.

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 0%, so the description must carry parameter meaning. It documents domain (new site's own domain, with example), key (optional short name, defaults to a slug), and confirm (preview vs create). However, the `server` parameter is never mentioned, leaving one of four parameters unexplained in both schema and description.

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+resource ('Adds ANOTHER website to the user's existing server, on its own domain') and explicitly distinguishes this from the alternative of buying a second server. It also implicitly separates itself from siblings like create_trial_site, scaffold_site, and remove_site.

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?

Gives explicit when-to-use guidance ('Use this instead of telling them to buy a second server') and routes the follow-on step to a named sibling ('Then write the pages with site_write_file'). It even covers the edge case where no registrar action is needed.

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