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

With no annotations, the description carries the full burden of behavioral disclosure. It states that the endpoint is public and requires no key, which is a genuine behavioral trait. But it does not disclose query type expectations, rate limits, response nature, or whether the tool performs a lookup, search, or aggregation — critical gaps for a breach tool.

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 is a single short sentence with no filler. It communicates the service and the key requirement efficientlyholistic. It is appropriately sized, though some brevity could be sacrificed for parameter clarity.

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?

Despite having an output schemalor and only one parameter, the definition is critically incomplete. The input parameter semantics are entirely opaque, and the absence of usage guidance makes this tool less likely to be selected correctly. An output schema cannot compensate for missing input semantics.

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?

The schema has one parameter (q) with no description (0% coverage), and the tool description likewise provides no hint about what q should contain. An agent cannot infer whether q expects an email address, username, IP, or something else. The description completely fails to compensate for the missing schema documentation.

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 service (leakcheck.io) and the general category (breach exposure), and explicitly notes no key is required, which distinguishes it from keyed breach tools. However, it lacks a clear verb like 'search' or 'check' and does not explain what the query parameter q represents (email, username, domain, etc.), so an agent cannot tell exactly what operation will be performed.

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?

No guidance is provided on when to use this tool versus the many sibling breach tools (breach_aggregator, breachdb, comb_search, hibp, leaklookup, etc.). The 'no key' hint is useful but insufficient to route an agent to this tool over alternatives.

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