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

Annotations already declare readOnlyHint=false, idempotentHint=true, destructiveHint=false and openWorldHint=false, so safety and idempotency are covered structurally. The description adds genuine context by restating the idempotent return behavior and disclosing the plan constraint ("The free plan includes one website"), but never says what happens when the limit is exceeded or the token is stale, nor what object is returned.

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?

Three sentences, front-loaded with the action and precondition, then defaults, then idempotency, then the plan limit. Every sentence carries a distinct fact, though the hostname-default sentence partially duplicates 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 two-parameter mutation with annotations and no output schema, the description covers precondition, defaulting, idempotent behavior, and the plan cap. The remaining gap is failure behavior and return value, which matters more here because no output schema exists.

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 both parameters are documented with defaults and length bounds, so the schema does the heavy lifting. The description only echoes the schema's hostname default and the setup_token source; it adds no syntax, format, or edge-case meaning beyond it.

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 and resource ("Adds the website to the confirmed account") and immediately scopes the precondition (setup_token must be ready). It also positions itself against create_account by explaining the hostname defaults to the website given there, so an agent can tell which sibling precedes it.

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 parenthetical "setup_token must be ready" gives an explicit precondition, and "An already added website is returned as is" tells the agent it is safe to call on a repeat. No alternatives or explicit when-not guidance are given (e.g., which sibling to use to change the website later), so it stops short of a 5.

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