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

Annotations cover safety (readOnly=false, idempotent=false, destructive=false) but say nothing about cost, auth, or limits. The description adds critical behavior beyond them: free-only, never purchases a name, upload cap of 100 MB signed in, and the claim_url obligation for anonymous sites.

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 action and the file contract, then the token/site_id logic. Slightly padded by three overlapping sentences forbidding purchases ('Never buy... without asking'), which restate one policy point.

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?

No output schema, but the description covers the one return-relevant item an agent needs (claim_url), plus auth modes, size limits, and folder-selection rules. Nothing needed to invoke it correctly is missing.

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 already 100%, so baseline is 3, but the description adds real meaning: site_id's reserve-vs-create semantics and the slug 'errors when taken' behavior are not fully spelled out in the schema. Inline file/encoding expectations are reinforced.

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?

Opens with a specific verb+resource+scope: 'Put a static site online on a free link.' It clearly distinguishes itself from siblings like list_sites, point_domain, and get_checkout_link by describing the actual deployment action.

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?

Explicit routing rules: use a token + site_id to update, omit site_id to fill the oldest reserved address, omit the token to go live anonymously. It also tells the agent not to pick the folder itself and to hand the human a claim_url in anonymous mode — genuine when/when-not guidance.

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