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

Annotations already declare the safety profile (not read-only, not idempotent, not destructive), so the bar is lower; the description still adds real behavioral context by disclosing that the new site counts toward the plan's site limit, which is quota information an agent cannot get from annotations. It also advises that single-file HTML with inline CSS/JS works best. It does not mention name-collision behavior or failure modes.

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?

Two short sentences, zero waste, with the concrete outcome (the generated URL) front-loaded and the caveats trailing. Every clause earns 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 two-parameter create tool with no output schema, the description covers the outcome (created URL), quota impact, and HTML format guidance. It stops short of saying what is returned or what happens on subdomain collision, which are minor gaps.

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 100%, so the baseline is 3. The description adds the practical hint that inline CSS/JS in a single file is the best format for the html parameter, but repeats the optionality and size constraint already documented in the schema.

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 and resource ('Creates a new website') and even shows the resulting URL pattern https://<name>.hostilo.app, which makes it immediately distinguishable from update_site and the read-only siblings. An agent knows exactly what this tool produces.

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?

Implies creation context and notes HTML is optional, but gives no explicit when-to-use guidance relative to alternatives such as update_site, nor any prerequisites for choosing this over them. Usage is inferable but not stated.

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