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

Annotations already flag destructiveHint=true and idempotentHint=true, so the description's job is to explain why. It does exactly that: domains overwrites the entire allow-list and 'the bubble stops loading on any address left out' — a concrete, non-obvious failure mode an agent would not infer from the schema. Still silent on whether omitted fields are left unchanged and on permission requirements.

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?

One dense but well-ordered sentence: the field list first, then the domains/add_domains contrast and its warning. No filler, and the highest-risk information is placed where the eye lands.

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 an 8-param mutation tool with no output schema, the definition covers the one parameter pair that can cause real damage. The remaining gap is partial-update semantics: nothing states that unspecified fields are preserved, which matters for an idempotent-but-destructive update.

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 baseline is 3; the description earns a step up by disambiguating the two easily-confused domain parameters and spelling out the operational consequence of the replace option. Nothing is added for position, theme, or greeting_enabled beyond what the schema already states.

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 ('Changes') and resource ('a website'), then enumerates the mutable fields (name, color, position, theme, greeting_enabled). Combined with the sibling list, which is dominated by get_/list_ readers and a separate create_site, an agent can place this immediately as the mutation path.

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 gives explicit param-level decision guidance: add_domains appends, domains replaces everything. That is a genuine 'use A vs B' rule. It stops short of tool-level guidance (when to update vs recreate via create_site, or required permissions), so not a 5.

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