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

Annotations already cover the safety profile (readOnlyHint=true, openWorldHint=true), so credit goes to the extra disclosure that the check does not reserve the name, which is a real behavioral caveat for a read-only probe racing against create_site. It does not explain what the response says or how failures/rate limits appear, keeping it below a 5. Note the destructiveHint=true annotation is odd for a read-only check, but the description does not contradict it.

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 short sentence with a colon that front-loads the core question and then adds the naming constraint and the reservation caveat. No filler, nothing repeated from the schema example.

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 with no output schema, the definition should say what the result looks like (a boolean, an availability object, error on taken names). It covers the identifier format well but leaves the return contract entirely implicit.

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 100% and already documents the single 'site' parameter with the jane.pixelglass.me example. The description adds genuine meaning by specifying the allowed character set (letters, numbers, hyphens) and confirming the parameter is only the label, not a full domain.

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 resource and check: whether a site address (the label before .pixelglass.me) is free. It also contrasts with create_site, which is the operation that actually reserves the name, so an agent can distinguish it from the write path. It is clear but phrased somewhat telegraphically rather than as a crisp verb-first sentence.

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?

Usage is implied rather than stated: 'Nothing is reserved; create_site reserves it' hints this is a pre-flight availability check before calling create_site, but there is no explicit 'use this when' or 'consider check_domain instead' guidance. Among siblings like check_domain and site_status, the boundary is only partially drawn.

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