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

Discloses a real side effect not present in annotations or schema: the old handle is released. It also explains the preview/confirm gating behavior. Annotations already declare idempotentHint=true and destructiveHint=false, and the description neither contradicts nor duplicates them; it simply does not mention auth requirements or the taken-handle failure mode.

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 mutation and its constraints, then the prerequisite tool, then the two-step protocol. No filler and nothing important buried at the end.

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 no output schema, the description covers format, prerequisite validation, side effect, and the confirm flow — everything needed to invoke it correctly. It stops short of noting failure cases or downstream effects on existing links/mentions, which is a minor gap.

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 the baseline is 3, but the description adds validation semantics the schema omits entirely: 3-20 characters, lowercase letters, numbers, underscore. The confirm_token workflow is described in both places, so that half adds no new meaning.

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 precise verb+resource (change your @handle) and immediately constrains it with the character/length rules, so the agent knows exactly what the tool mutates. It is unmistakably distinct from check_username, the sibling it names, which only validates rather than changes.

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?

Explicitly routes the agent to check_username first, then lays out the required two-call confirmation sequence including the 'only after they agree' condition. Both the when-to-use and the ordering prerequisite are stated rather than inferred.

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