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

Annotations already declare readOnlyHint=true and destructiveHint=false, yet the description adds substantive context: the edit_theme_options capability requirement, the hard refusal on block themes, and the fact that legacy widget types return null settings with settings_editable=false and are read-only over MCP. It also discloses the "runs straight away" behavior through Royally. Nothing here contradicts the annotations.

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 purpose, then parameters, then return shape, then alternatives and prerequisites — a sensible ordering. It is dense and slightly overstuffed (the Royally read-only sentence is close to redundant with the annotation), but no sentence is filler.

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 detailing the return payload (widgets array with id, id_base, sidebar, position, settings_editable, settings, plus total) and explaining that position is the 0-based index accepted by wp_create_widget/wp_update_widget is exactly the missing context an agent needs to chain calls.

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 schema already documents both parameters. The description still adds value by naming the source of the sidebar id (wp_list_sidebars) and giving concrete examples ("sidebar-1", "wp_inactive_widgets"), which lets an agent pick a valid value without a second lookup.

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?

Opens with a specific verb and resource ("Lists the widgets placed in a classic theme's widget areas, with their settings") and immediately scopes it to classic themes. The later clause distinguishes it from wp_get_widget (single widget with rendered HTML) and wp_list_templates (block themes), so an agent can route without opening schemas.

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?

Explicitly states the omit-to-list-all vs pass-sidebar-to-filter behavior, names wp_get_widget for single-widget retrieval and wp_list_templates as the fallback when the theme is a block theme, and notes the tool is refused in that case. It also names the required capability (edit_theme_options), covering the prerequisite an agent would otherwise discover by failing.

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