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

The readOnlyHint annotation already establishes this is a safe read. The description adds genuine context beyond that: results are scoped to the developer account's accessible sites, and passing site_ids returns more detail per site. Minor gaps remain around pagination/return shape, but the added behavioral detail is real.

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 tight sentences, front-loaded with the core action, followed by the alternate mode, a usage hint, and the underlying endpoint. No filler; every sentence carries distinct information.

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 no-required-param, read-only list tool with fully documented parameters, the description is nearly sufficient. Since no output schema exists, it does not describe what a site record contains, but for a listing/count tool that omission is minor.

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%, so limit, offset, and site_ids are fully documented in the schema. The description reinforces site_ids ('details for specific site ids') and its detail difference, but adds no syntax beyond the schema. Baseline 3 is appropriate.

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 (List) and resource (Mindbody sites/businesses), with the scope clarified as 'your developer account can access' and an alternate mode for 'specific site ids'. It is the only site-listing tool among the siblings, so disambiguation is trivial for an agent.

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?

Offers one concrete use case – 'a cheap way to confirm the API key works' – which implies when to reach for it, but there is no explicit when-not-to-use, no prerequisites, and no named alternatives. Usage is implied rather than stated.

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