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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is known. The description adds behavioral context by specifying the return shape (per-TLD status and aggregate counts) and the scope (core TLDs), which goes beyond the annotations. It doesn't contradict annotations.

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 two sentences, front-loaded with the action, and includes a compact pointer to related tools. Every sentence contributes value; no redundancy or filler.

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?

This is a simple read-only tool with one parameter and an output schema present. The description sufficiently communicates what it does and what it returns, and the output schema handles detailed return values. The mention of 'core TLDs' and aggregated counts completes the contextual picture without being verbose.

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 schema description for the single 'prefix' parameter is highly detailed ('Keyword without extension, e.g., openai'), providing 100% coverage. The tool description adds no parameter-level detail, so the schema carries the full burden. Baseline of 3 is appropriate.

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 clearly states the tool checks registration of a prefix across core TLDs and returns per-TLD status plus aggregate counts. It uses a specific verb ('check') and resource ('prefix across core TLDs'), and explicitly names related tools (bulk_tld, available), distinguishing its cross-TLD scope from bulk and single-TLD alternatives.

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 provides clear context for when to use this tool: when you need to see how a prefix is registered across multiple TLDs. It names related tools (bulk_tld, available) as alternatives, but stops short of explicit 'use this instead of X when...' guidance. Still, the purpose and related tools give enough signal for appropriate selection.

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