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

Annotations already cover read-only, idempotent, non-destructive, and open-world behavior. The description adds meaningful context beyond them: the enumeration of checked TLDs, brandable variations, the shape of the result (available / price / taken), and that no login is required. It does not discuss rate limits or pricing freshness, keeping it just under a 5.

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?

Front-loaded with purpose and invocation trigger, then structured into numbered routing rules. The long TLD enumeration and some repetition of the full-domain rule cost a little length, but every sentence carries routing or scoping information.

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 correctly explains what comes back (availability, yearly price, taken). For a single-parameter search tool it covers trigger conditions, parameter form, correction behavior, and a negative case — nothing an agent needs is missing.

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 coverage is 100%, so the baseline is 3, but the description adds real meaning: it distinguishes a bare base word from a full domain and gives concrete examples of when each form applies, plus a strong "never strip or substitute the TLD" rule for corrections. The schema description largely mirrors this, so it is reinforcement rather than new information.

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?

States a specific verb and resource ("Search domain-name availability and pricing") and enumerates the exact extensions checked, so an agent can distinguish it from list_my_domains or lookup_whois at a glance. It also states what is returned (availability, yearly price, taken status).

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?

Explicitly says when to call ("CALL THIS whenever the user wants to find, check, buy, or register a domain") and gives three concrete routing rules, including an explicit when-NOT-to-call case for users merely reacting to results. Alternatives (answer from prior results) are named.

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