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

Annotations already declare it as a non-readonly, idempotent, non-destructive mutation, so the safety profile is covered. The description adds one genuinely useful constraint (subdomain is immutable after creation) but says nothing about permissions, failure modes, or whether omitted fields are left untouched.

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?

Two tight sentences: the capability and its constraint come first, the when-to-use trigger second. Every clause carries information and nothing is repeated from the schema.

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 small 3-parameter mutation with complete annotations and no output schema, the description covers scope, editable fields, and the key immutability constraint. Only return behavior and any permission requirements remain unstated, which is acceptable here.

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 every parameter (siteId, name, locale) is already documented in the schema with enums and length bounds. The description only restates which fields are editable, adding no format or validation detail beyond the schema.

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 concrete verb (update) plus the exact editable fields (display name, language), and adds the negative scope that the subdomain cannot be changed. It doesn't explicitly contrast with close siblings like update_domain_settings or set_site_url, so it stops just short of full differentiation.

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 an explicit when-to-use clause: renaming a page or switching its locale (ja/en). It also implicitly rules out subdomain changes, but never names an alternative tool or excludes any other scenario, so no 5.

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