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

readOnlyHint=true already declares this as a safe read. The description adds useful context about what the result conveys (plan eligibility, recommendation, already-added status), which is more than the annotation provides, but it says nothing about auth requirements, pagination, or how 'recommended for this site' is determined.

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 resource and its key differentiator. It is a sentence fragment rather than a complete statement, but no words are wasted.

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, describing the returned fields is exactly the right use of the description, and readOnly covers the safety profile. The main gap is the missing action verb and any usage routing, but nothing critical to invoking the tool is absent.

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?

Single siteId parameter with 100% schema description coverage, so the schema already documents it. The description adds no meaning about the identifier's format or scope, which is the expected baseline when the schema carries the burden.

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 the resource (checks) and scopes it to checks that can be added to a site, which distinguishes it from add_checks/update_check. However it never states the verb explicitly ('list'/'retrieve') and reads more as a return-shape description than an action statement.

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?

No when-to-use guidance, no prerequisites, and no mention of alternatives such as add_checks or update_check. The agent must infer that this is the pre-flight lookup before adding checks.

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