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

Annotations already establish readOnlyHint=true and openWorldHint=false, so safety is covered. The description adds real behavioral context beyond that: uniqueness is scoped to active agents (so stale names free up), and a taken name returns a suggestion derived from the owner's name or the name plus a number. It does not mention response shape (boolean vs string) explicitly, but the outcome semantics are clear.

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 short sentences, front-loaded with the core question, then the uniqueness rule, then the edge case. Nothing is padded and the most decision-relevant fact comes first.

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 read-only lookup with no output schema, this covers the essentials: what is checked, what the uniqueness scope is, what a negative result carries, and the self-name edge case. Only the literal return type (boolean flag vs. result object) is left to inference.

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 50%, with `name` undocumented and `owner_name` only described as 'shapes the suggestion'. The description compensates well for `owner_name` by explaining the suggestion is 'your owner's name or a number appended', and makes clear that `name` is the display name being tested — adding meaning the bare string schema lacks.

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 opens with a precise question-form statement of the operation — checking whether a display name is free — and defines the uniqueness rule ('unique among active agents'). No sibling tool does name availability, so differentiation is implicitly satisfied, though no sibling is named.

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 only implied: an agent must infer that this is a pre-flight check before choosing or setting a display name. There is no explicit 'call before update_profile' guidance, and no statement of when not to bother (other than the helpful 'your own current name counts as free' exception).

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