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

Annotations already declare readOnly/idempotent/non-destructive, yet the description adds genuinely non-obvious behavior: sensitive values are redacted, and 'writable' is defined precisely as theme-writes-on plus allowlist membership. That is real value beyond structured fields. It omits what happens for an unknown mod name (error vs exists=false).

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 action and return shape in a single dense sentence; every clause (exists, redaction, writable) is informative. The trailing site URL and 'Through Royally: read-only, runs straight away' partly restate the readOnlyHint annotation, which is mild waste.

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 usefully enumerates the three returned facets (exists, value, writable) plus the redaction caveat, which is exactly what an agent needs to interpret the response. The main remaining gap is behavior on a nonexistent or misspelled mod name.

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 site_id enum is self-documenting, so the schema carries most of the weight. The description reinforces that mod_name is a single mod looked up by name, and the schema points to wp_get_theme_mods for the valid name list, but no format or casing details are added.

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?

"Get one customizer setting (theme mod) of the active theme by name" is a specific verb+resource, and it explicitly names the companion write tool (wp_update_theme_mod) in the writable explanation. It stops short of explicitly contrasting itself with wp_get_theme_mods (the plural lister), which is only referenced inside the mod_name schema description.

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 writable field ties this tool to a clear workflow: call it before wp_update_theme_mod to confirm the mod is in the allowlist and theme writes are enabled. "Runs straight away" clarifies there is no confirmation step. It never states a when-not or an explicit alternative for enumerating mods, so it is context-rich but not fully routing.

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