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

Annotations already declare readOnlyHint, idempotentHint and destructiveHint=false, so the safety profile is covered. The description still adds a non-obvious behavioral trait beyond the annotations: that the tool suggests alternatives when the name is taken, which tells the agent to inspect the response rather than only reading a boolean.

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?

A single sentence with no filler, front-loading the availability check and appending the fallback behavior. Nothing is wasted and nothing important is buried.

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 probe with no output schema, the description covers what is checked and the fallback behavior. It omits pagination/format details and any explicit linkage to create_page, but those are minor given the tool's simplicity.

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% for the single 'username' parameter, so baseline is 3. The description adds marginal meaning by showing the parameter is interpolated into the 'lnx.net/<username>' path, clarifying expected format and scope of the check.

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 (checks) and a specific resource (lnx.net/<username> availability), which is unambiguous on its own. It does not, however, name or contrast itself with the sibling create_page, which is the obvious companion tool.

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 only implied: an agent can infer this is a pre-flight check before create_page, but the description never says when to call it versus the sibling or whether it is a prerequisite. No exclusions or ordering guidance are given.

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