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

Annotations already declare this a read-only, idempotent, non-destructive operation, so the safety profile is covered. The description usefully adds the scope of the uniqueness check ("one of the user's sites"), but it omits a meaningful caveat: a passing check does not reserve the name, so a subsequent create could still fail. For a validation tool that gap matters and is not disclosed.

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 sentence, front-loaded with the action, with no filler or repetition of the title. Slightly wordy in the tail ("by one of the user's sites") where "the user's sites" would suffice, but there is no wasted structure.

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 tool with an output schema and full annotation coverage, the description supplies enough to call it correctly. The only shortfall is the missing statement of when in a workflow to invoke it and how to interpret a negative result.

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% with a single well-labeled property, so the schema already carries the parameter meaning; the description adds nothing beyond the phrase "site name." Baseline 3 applies when the schema does the heavy lifting.

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 pairs a specific verb ("Check") with a specific resource ("site name") and names the two conditions tested: syntactic validity and uniqueness against the user's existing sites. It is clearly distinguishable from siblings like list_sites or get_site_details, though it never names an alternative 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 validation call before deploy_site or site creation, but the description never says so. There is no explicit when-to-use, no statement that it is optional or recommended, and no named alternative for name-existence questions.

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