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

With no annotations, the description carries the full burden; it does disclose the important behavioral trait that output is neutral factual data rather than a ranking, which is real value. It does not say whether the operation is read-only (implied but unstated), how it behaves with an unknown or duplicate slug, or how the results are ordered.

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 short clauses, zero padding, with the scope (2–4 listings) front-loaded ahead of the caveat. Every phrase earns its place.

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 single-parameter read-style comparison tool with no output schema, the description covers what it does, the input cardinality, and the nature of the result. The remaining gap is what attributes are compared and how results are ordered, which would help an agent decide whether to call it at all.

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?

Only one parameter and schema description coverage is 100%, so the schema already documents the slugs array with minItems 2 and maxItems 4. The description's "2–4 listings" merely restates those bounds and adds no format, ordering, or validity semantics.

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?

Specific verb (compare) plus a named resource (Agent Index listings) and an explicit cardinality bound of 2–4, which implicitly separates it from the single-item get_agent and the broader search_agents. It stops short of naming a sibling, so differentiation relies on inference.

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?

"Compare 2–4 ... side by side" implies the use case (evaluating multiple agents at once) and "not a ranking or recommendation" signals what the tool is not for. There is no explicit statement of when to prefer it over search_agents or chained get_agent calls, leaving the alternative-selection decision to the agent.

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