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

Annotations already declare readOnlyHint=false, destructiveHint=false, and openWorldHint=false, so the safety profile is covered. The description adds the non-obvious side effect that the new site becomes the active site, which is meaningful state-change context beyond the annotations. It stops short of disclosing failure behavior, uniqueness constraints, or quota limits.

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?

A single front-loaded sentence with no filler. The side effect is placed at the end where it naturally follows the core action, and nothing is redundant.

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 simple 3-parameter creation tool with full schema coverage and annotations, the description covers the action, target, and side effect. It omits the 'lng' parameter and any failure/duplicate-address behavior, but no output schema exists so return values need not be explained.

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%, with the 'dom' enum codes fully mapped to hosts and 'addr'/'lng' constraints documented in the schema. The description only restates 'at the given address and zone' without adding format or validation detail, so baseline 3 applies.

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?

Uses a specific verb+resource ('Creates a new uCoz site') and states scope (signed-in account) and side effect ('makes it the active site'). An agent can distinguish it from list_sites and select_site purely from the 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?

Usage is implied by the verb — this is the only site-creation tool among siblings, so no alternative needs naming. However, it gives no prerequisites (auth requirements, whether the address must be free, quota limits) and no explicit when-to-use framing.

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