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

Annotations already signal a safe, open-world read (readOnlyHint, openWorldHint), so the bar is lower. The description still adds real value by disclosing what comes back: availability, first-year and renewal prices, and an order link. With no output schema, this return-value summary is the main source of behavioral context, though rate limits or failure modes are unmentioned.

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?

Two tight sentences, with the core purpose and return content front-loaded before the input guidance. No padding, though the parenthetical example slightly duplicates the schema example.

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 two-parameter, read-only lookup with full schema coverage, the description covers purpose, input format, and output contents. Only minor gaps remain, such as pricing currency caveats already stated and the absence of any note on behavior when a domain is invalid.

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 both parameters are documented with examples and the default ext of .com. The description's 'full name or name plus up to 5 extensions' largely restates the schema, adding only the either/or framing. Baseline 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 states a specific verb and resource (checks whether a domain can be registered) and even summarizes the return payload (first-year and renewal prices in BDT, order link). It does not explicitly distinguish itself from the sibling domain_prices, which also appears to be price-related, so an agent could confuse the two.

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?

Usage is implied: check availability before ordering. The second sentence gives input-format guidance (full name or name plus up to 5 extensions), which is useful. However, there is no explicit when-to-use versus domain_prices or order_link, and no stated preconditions or exclusions.

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