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 adds genuinely useful context beyond that: the authentication requirement (site key as Bearer token) and the shape of the returned status data.

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 padding, and the payload (what the caller gets back) is front-loaded before the auth note. Nothing in the description is redundant filler.

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 annotations covering safety, an output schema covering return values, and full schema coverage on the sole parameter, the description supplies everything else an agent needs (resource identity, returned fields, auth). Only the absence of any when-to-use routing against siblings keeps it from being fully complete.

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% and the single site_key parameter is fully documented in the schema, including the maxLength/minLength constraint and the fact that the Authorization header takes precedence. The description's mention of the Bearer token overlaps with that schema text rather than adding new meaning, so baseline 3 applies.

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 concrete resource (the caller's site) and enumerates exactly what it returns: URL, plan, remaining messages and images for the period. It reads clearly as a status/read tool and is distinguishable in spirit from create_site or talk_to_emma, though it never explicitly contrasts itself with those siblings.

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: the agent can infer this is the tool for checking plan/quota status, and the description adds one prerequisite (site key as Bearer token). There is no statement of when to prefer this over siblings like confirm_site, nor any exclusion conditions.

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