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

Annotations already cover readOnly/idempotent/non-destructive, so the bar is lower; the description still adds real behavioral value by disclosing result ordering ("Verified lines, whose address is a domain its owner proved, come first") and that listings are opt-in. It doesn't mention result limits, pagination, or empty-result behavior, which holds it below 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?

Three sentences, all carrying content: eligibility of listings, ranking order, and search modes. There is mild redundancy between "what each one is for and what you can call it about" and "by what the call is about", and the colloquial framing costs a few words, but nothing is gratuitous.

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 three optional parameters, no output schema, and rich annotations, the main missing piece is what a listing actually returns. The description partially compensates ("with what each one is for and what you can call it about"), but an agent still doesn't know the result fields or volume. Otherwise complete for a read-only search.

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% and both enum parameters are documented in the schema, so the baseline is 3. The description restates the three search modes but adds only marginal nuance ("a person, or a business's industry" for category, "what you can call it about" for ask_about) beyond what the schema descriptions already say.

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 names the resource (directory listings of people, AIs, businesses) and the operation (search by words, by kind, or by what the call is about). It reads somewhat indirectly at the start ("Who's on the network") before landing on the search verb, but an agent can still tell this apart from join_directory or listing_link. It is clear, though the operative verb arrives late.

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?

"Any of them can be called" implies the downstream purpose — find an entry, then use the call tool — which is useful routing context. However, no explicit when-to-use/when-not or naming of alternatives (join_directory, listing_link, allow/block) is given. Usage is implied, not spelled out.

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