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

Annotations already declare readOnly, idempotent, non-destructive, and closed-world, so the safety profile is covered. The description meaningfully adds that no token is required and enumerates exactly what is returned, which matters because there is no output schema; it does not cover error behavior for an unknown slug.

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?

Three short sentences, front-loaded with the return payload and no filler. 'Input: slug' is mildly redundant with the schema but the phrasing is tight overall.

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?

With no output schema, the description correctly carries the burden of describing return fields, and it notes the auth situation. For a one-parameter read tool this is close to complete, missing only failure behavior for a nonexistent slug.

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 the single parameter is documented in the schema, so the baseline of 3 applies. The description's 'Input: slug' merely restates the schema without adding format or lookup-resolution details.

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 names a specific verb (returns) and a specific resource (a site's liveness plus URL, version, size, timestamps), which an agent can easily distinguish from list_sites or delete_site. It stops short of naming a sibling explicitly, but the field-level detail makes the scope unambiguous.

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 the single-slug lookup versus the listing tool, but there is no explicit statement of when to prefer it over list_sites or get_manifest, and no exclusions or prerequisites beyond the token note.

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