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

Annotations already flag destructiveHint=true and readOnlyHint=false, but the description adds substantial context beyond them: old addresses redirect for a year and stay reserved, a site can move at most 3 times a year, and the `outcome` field reports created/moved/unchanged. This is exactly the kind of side-effect and rate-limit disclosure annotations cannot carry.

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 and the 'rarely needed' caveat, then organized into scannable bullets covering each branch. Despite its length, every sentence carries actionable information (redirects, reservation, move limit, outcome values), so nothing is wasted.

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 single-parameter mutation tool with a 100%-covered schema and an output schema, this description covers everything an agent needs: when to call it, when it's a no-op, what it destroys, and what the outcome field means. Return-value detail is rightly left to the output schema.

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 description coverage is 100%, so the baseline is 3, and the schema already documents the handle-derivation fallback. The description adds the no-op semantics ('No `subdomain`, or the current one: changes nothing') and the address-mapping example, which goes 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?

The description states a specific verb+resource ('Choose the address of the user's site, or change it') and immediately distinguishes itself from siblings by noting create_page already creates the site and get_account shows the current address. An agent can tell exactly what this tool does without opening the schema.

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?

It explicitly frames the tool as 'Rarely needed', names the alternatives (create_page, get_account), and gives the precise conditions under which each branch fires: no site yet, site already exists, or no subdomain/current one. It even instructs the agent to ask the user first and remind them about the Instagram bio link.

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