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

Annotations already declare readOnlyHint=true and destructiveHint=false; the description goes further by explaining that omitting wpcom_site yields a siteless catalogue with null checkout_url, while supplying it adds intro offers, downgrade paths, and a bound checkout_url. That is real behavioral context beyond the annotations. The trailing fragment about the server marking it read-only is redundant with the hints and garbled, which caps the score.

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?

The key scope and the wpcom_site fork are front-loaded, which is good, but the body is a single dense paragraph that mixes return-shape, usage, and mini-tutorials. The truncated '… Through Royally: its server marks it read-only' tail is incoherent filler that costs the reader attention.

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 carries the burden of explaining returns, and it does reasonably well: plan rows, prices in user currency, entitlements mapping features to tiers, storage in GB, and per-site enrichment fields. Defaults for currency and interval are left mostly to the schema, and the tail noise slightly muddies an otherwise complete picture.

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 wpcom_site schema text already spells out the intro offers / downgrade paths / checkout_url behavior almost verbatim, so the description largely restates structured data. It does imply currency defaults ('prices in the user's currency') but adds nothing for interval; baseline 3 is warranted when the schema does the heavy lifting.

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?

Names a specific verb and resource ('Returns the WordPress.com hosting plan catalogue') and enumerates the tier set plus the payload contents (prices, entitlements, storage in GB). It is clearly distinguishable from sibling commerce tools like wpcom-checkout-url and wpcom-domain-purchase, since this is a read-only catalogue rather than a purchase action.

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?

Gives concrete usage contexts with example user questions ('how much does WordPress.com cost?', 'can I install plugins?') and even procedural guidance inside the tool ('For capability questions, use entitlements: find the group containing the feature'). It states the behavioral fork for passing vs. omitting wpcom_site, but never names a sibling alternative or an explicit when-not-to-use.

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