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

The annotations already declare readOnlyHint=true and destructiveHint=false, so the safe read-only nature is known. The description adds valuable context beyond annotations by specifying the domain (unu.lu), providing an example that demonstrates the mapping to a subdomain, and mentioning that it checks availability for claiming. No contradictions detected.

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?

The description is three sentences, each serving a distinct purpose: state the core function, give a concrete example, and provide usage context. It is front-loaded with the main action and contains no redundant or filler content.

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 tool with one parameter and an output schema, the description fully covers what the tool does, how to use it, and why. The example and usage guidance make it complete. The output schema handles return details, so no further explanation is needed.

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?

The input schema already documents the handle parameter with constraints, achieving 100% coverage. The description adds semantic meaning by explaining that checking 'joe' tells you if joe.unu.lu is available, clarifying the domain format and the intent of the parameter beyond the schema's simple 'handle to check'.

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 uses a specific verb 'Check' and identifies the exact resource: handle availability on unu.lu. It distinguishes itself from siblings by explicitly noting 'not other platforms like Instagram, TikTok, etc.' and provides a concrete example ('joe' -> joe.unu.lu), making the purpose immediately clear.

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 description states when to use the tool: 'Use this to help users choose a handle before they visit the claim page.' It also clarifies the scope, explicitly excluding other platforms, which prevents misuse. This is direct usage guidance without needing to reference sibling tools.

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