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

With no annotations provided, the description carries the full transparency burden. It discloses live registry verification, that only available domains are returned, grouping by TLD, and default TLDs. It doesn't mention rate limits or error handling, but for a simple read-only enumeration tool, this is strong behavioral disclosure, earning a 4.

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?

Four sentences efficiently convey the purpose, differentiator, position examples, behavioral verification note, and default TLDs. It is front-loaded with the core value proposition and contains no filler—every sentence earns its place.

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 4-parameter tool with no output schema, the description covers the operation, parameter behavior, defaults, and output grouping ('grouped by TLD'). It doesn't specify the exact return structure, but given the straightforward nature, it is sufficient for an agent to invoke the tool correctly—slightly more detail on return format would push it to a 5.

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 covers 100% of parameters, so baseline is 3. The description adds concrete examples for the 'position' enum (e.g., 'starts' → 'Bearoak') and clarifies comma-separated keyword lists, which meaningfully supplements the bare schema definitions and justifies a 4.

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 states a specific action ('exhaustively enumerate') on a specific resource ('available domain matching a keyword PATTERN') and immediately differentiates it from other domain tools by highlighting its exhaustive, cross-TLD nature. It also explains the pattern positions, making the tool's function unmistakable even without opening the schema.

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?

It clearly implies its unique niche—exhaustive pattern-based enumeration across TLDs, contrasting with 'most domain tools'—and gives usage context with positions and defaults. However, it does not explicitly name sibling alternatives (check_domain, find_available_domains) or specify when NOT to use this tool, so it stops short of a 5.

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