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

Annotations already indicate readOnlyHint and openWorldHint, and the description adds meaningful behavior beyond those: cached ideas receive a new availability check, and unknown availability/registration quotes are null and never reused from an old search. This gives the agent an accurate model of data freshness and result reliability. No contradiction with annotations exists.

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 five sentences long, dense but largely purposeful: main function, result contents, freshness behavior, null handling, and an alternative tool reference. Every sentence contributes, though phrases like 'any domain hacks supplied by the source' are slightly awkward and the sentence about cached ideas could be tightened. It is efficient without being minimal.

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 does a good job explaining what callers get back: brandable names, domain hacks, availability, monthly keyword search-volume where available, and registration quotes with null fallback. It also explains data freshness and where to go for a fresh quote. It still leaves some details unstated, such as exact response shape, ordering, or limits, but these are less critical for a brainstorming tool.

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 has 100% description coverage, so the baseline is 3 and the schema already documents idea, tlds, purpose, and description. The description adds only a light tie between the idea parameter and 'an idea, product, or company' and does not materially deepen understanding of the other parameters. It does not need to compensate for a schema gap because none exists.

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 and resource: 'Brainstorm domain names for an idea, product, or company.' It clearly distinguishes the tool from siblings by emphasizing both generation of brandable names/domain hacks and availability data, and it explicitly points to search_domain for a fresh quote. The purpose is unambiguous and differentiates from check_availability and search_domain.

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 usage context: it is for brainstorming domain names rather than getting a final quote. It explicitly says 'Use search_domain for a fresh quote or follow the registrar link,' which routes the agent away from this tool for that need. However, it never mentions the check_availability sibling or says when to use that instead of this tool, so the alternative guidance is incomplete.

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