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

Annotations already provide readOnlyHint, idempotentHint, and destructiveHint, so safety is covered. The description adds genuinely useful behavioral context beyond those hints: results are 'unranked candidates,' prices are decimal strings, return fields are named, and 'No auth required' is stated. This meaningfully helps an agent anticipate behavior without contradicting the 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 compact and front-loaded with purpose, then workflow usage, filters, and return shape. The repeated 'listCategorizedTlds:' prefix is slightly redundant, but every remaining sentence earns its place and there is no 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?

With no output schema, the description appropriately describes the returned shape: unranked candidates with categories, audience, prices, and flags. It also covers auth requirements and optional filters. Minor gaps remain, such as currency and pagination, but none of these block a correct call.

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 description coverage is 100%, so the schema already documents every parameter in detail. The description only summarizes them as 'price cap, exclude ccTLDs/restricted/premium, registry,' which adds no semantic depth beyond the schema. This matches the baseline-3 case where structured data carries the load.

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 specific verb-resource pair: 'List TLDs from the OSIR catalog that have category and audience metadata.' It clearly distinguishes this catalog-listing tool from pricing/extension tools and explicitly ties it to the bulkDomainSuggestions workflow, so an agent can tell exactly what it does and why it exists.

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 gives explicit when-to-use guidance: pick 3-6 relevant TLDs before calling bulkDomainSuggestions. It also describes the available filters, which shape usage. It stops short of naming alternative tools to avoid or explicitly excluding other catalog/list tools, so it earns a 4 rather than a 5.

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