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

Annotations already declare readOnlyHint=true, openWorldHint=false and destructiveHint=false, so the safety profile is covered by structured data. The description adds genuinely new behavioral facts beyond that: no new request, no charge, deterministic ranking order with a per-row `why` explaining each placement, and what happens when no stored answer exists. It stops short of describing row/pagination behavior or failure modes.

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 core scope and the no-charge guarantee are front-loaded in the first clause, followed by ranking logic, then the fallback. No sentence is filler; every clause carries either scope, cost, ordering, or escape-hatch 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 nonetheless explains the return shape (ranked rows with a `why` field), the ordering criteria, and the empty-state behavior. Combined with a fully documented schema, an agent has everything needed to call and interpret this 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 coverage is 100%, so the schema already carries baseline parameter documentation. The description still adds meaning beyond it by framing `competitors` as selecting among stored gaps rather than arbitrary domains, implying an unstored set will not be looked up, and by explaining that the ranking is applied to the returned set.

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?

Names a specific resource with scope: domains linking to competitors but not the client, drawn from a stored gap answer, ranked by usefulness. It also implicitly distinguishes itself from run_link_lookup by noting this reads storage rather than buying a new lookup, and from get_referring_domains by the gap framing.

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 states the no-cost/no-request condition that selects this tool, and names the alternative path: if there is no stored answer, call run_link_lookup with kind "gap" to buy one. Both the use case and the escalation path are spelled out.

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