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

Annotations already declare readOnlyHint=true and destructiveHint=false, and the closing sentence merely restates that ('its server marks it read-only, so it runs straight away'), adding no new behavioral information. What does add value is the return-shape caveat — the echoed mime_type_filter defaulting to an empty string and counts being INTEGERs rather than objects or numeric strings — which prevents real parsing mistakes.

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?

Front-loaded with the purpose, then the optional parameter, then the return shape — a sensible ordering. The final sentence about the Royally server being read-only repeats what annotations already say and is the one expendable clause.

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?

There is no output schema, so the description carries the burden of explaining the return value, and it does so concretely with a sample counts object and type clarification. For a simple two-parameter counting tool this is nearly complete; only the site_id default behavior and any scope caveats (e.g. whether trashed attachments are included) are left implicit.

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%, so the baseline is 3, but the description goes beyond the schema by documenting the round-trip behavior of `mime_type` (echoed back as `mime_type_filter`, "" when unfiltered). That is a real semantic detail the schema does not convey.

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 and resource: 'Returns attachment counts grouped by MIME type.' That clearly separates it from the media-listing siblings (wp_list_media, wp_find_media, wp_get_media), which return items rather than aggregates. It never names an alternative sibling explicitly, which keeps it short of a 5.

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?

The description explains the optional filter behavior but gives no explicit when-to-use or when-not-to-use guidance, and does not route the agent to wp_list_media or wp_find_media when item-level data is actually needed. Usage is implied by the purpose rather than stated.

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