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

The annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false, and openWorldHint=false, so the safety profile is covered. The description supplements this usefully by noting the read-only marking means the call "runs straight away" (no approval gate) and by describing what is returned. It does not discuss pagination behavior, result limits, or auth/scope failures, which would complete the picture.

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?

Four sentences, front-loaded with the core purpose and immediately followed by the usage guidance, so an agent gets the essentials first. The final sentence about "Through Royally" is somewhat awkwardly framed and reads like aggregator metadata, but it does convey a non-trivial behavioral fact (auto-approved read), so it earns its place despite the clumsy phrasing.

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 9-parameter, nested-schema, no-required, no-output-schema list tool, the description covers purpose, when to use, returned fields, and the read-only pre-approval behavior, while annotations and a richly-described schema cover safety and per-parameter semantics. Only return-shape details (e.g., pagination totals, default page size of 10) are left to the schema, which is acceptable since no output schema exists but the field list is named.

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 78%, just under the baseline threshold, so the schema carries most of the load and it already documents pagination, sorting, filters, platform, ownership, and environment in detail. The description only obliquely references parameters through the phrase "optional metrics" (include_metrics) and adds no format or interaction meaning beyond the schema. The 3 baseline is appropriate given the high coverage and lack of compensating detail.

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 opens with a precise verb+resource and scope: it lists the authenticated user's accessible sites across WordPress.com and Jetpack-connected self-hosted sites. It even enumerates the fields returned (blog IDs, URLs, names, platform type, MCP access status), which tells an agent what differentiates the output from the generic site lists among the 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?

It clearly states the tool's role: "Use this to discover which site IDs exist before calling site-scoped abilities," which is an explicit when-to-use. It also adds a display caution (use primary_domain, not site_url's host). What is missing is any statement of when NOT to use it or a named alternative, despite many sibling list tools (fleet__list_sites, recipe__fleet_inventory) that an agent could confuse it with.

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