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

The annotations already mark this as read-only, idempotent, and non-destructive, so the bar for additional disclosure is lower. The description adds useful context by specifying that it returns domains 'still available for registration' and lists concrete pattern shapes, which behaviorally clarifies the result set. It does not mention pagination or rate limits, but the schema parameter descriptions cover some of that (e.g., page depth).

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 consists of just two sentences: the first clearly states the tool's core function and any pattern caveats, and the second names related tools. It is front-loaded with the main purpose, contains no filler, and 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?

With an output schema present, the description does not need to explain return values. The tool has 8 optional parameters, and the description gives enough context about its scope (short .ai domains, pattern filtering, availability check). It could be more explicit about the relationship to 'available' and 'bulk_available', but overall it is complete for a read-only search 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?

Schema description coverage is 100%, so every parameter already has a description (type, sort, exclude, keyword, etc.). The tool description does not add extra meaning beyond what the schema provides; it only hints at pattern types (CVCV, CVCC) which are already enumerated in the type parameter. Thus, the 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 uses a specific verb+resource construction: 'Search unregistered short .ai domains by pattern' and details the pattern types (CVCV, CVCC, other 3-4 letter shapes). It also names related tools (available, bulk_available), which helps distinguish it from siblings that likely perform broader availability checks.

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 implies usage through its purpose statement and the 'Related: available, bulk_available' line suggests alternatives, but it does not explicitly state when to choose this tool over the related ones. There is no clear when-not-to-use guidance or differentiator beyond the pattern-search focus.

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