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

Annotations already declare readOnly, idempotent, non-destructive behavior, so the description is free to focus on output shape, which it does well: it lists the comparison dimensions and the mismatch-handling branch that returns a short explanation rather than an error. That edge-case behavior is genuinely useful context beyond the annotations, though it does not mention any limits or failure modes for bad slugs.

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 purpose is front-loaded in the first clause, and the enumerated output contents are dense and useful. The closing format sentence overlaps with the schema's format enum, a minor redundancy, but overall the description is efficient.

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 annotations covering safety and no output schema, the description is complete enough for an agent to know what it will receive and how mismatched pairs are handled. It could add guidance on resolving invalid slugs or when comparison is preferable to two single lookups, but the core behavior is covered.

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 both listing identifiers and the format enum are already fully documented. The description only restates the format options (markdown default, slim, json), adding slight emphasis on the default but no syntax or behavior beyond the schema; baseline 3 applies when the schema does the heavy lifting.

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 operation (two listings head to head) and enumerates exactly what the output contains: category-by-category scores, side-by-side facts, verdicts, agent notes. It is clearly distinguishable from single-listing siblings like get_tool because it explicitly takes a pair and frames the result as a comparison.

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?

Usage is implied by 'two listings head to head' and the note that mismatched pairs get a short explanation, but there is no explicit when-to-use statement or routing to alternatives such as calling get_tool twice or using search_tools to resolve slugs. The schema mentions search_tools for slugs, but the description itself offers no such guidance.

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