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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint, and destructiveHint=false. The description adds meaningful behavioral context: it scans paginated results server-side (implying potentially slower execution), computes exact intersection counts, and enforces a strict data accuracy contract with explicit prohibitions on hallucinating metrics. This goes beyond the annotations without contradicting them.

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 longer than typical but is front-loaded with the core purpose and then adds necessary operational details (pagination, compact totals) and a critical data-accuracy contract. Each sentence serves a purpose, though the contract could be slightly more concise. It is well-structured and not padded.

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?

Given the tool's complexity (11 optional params, no output schema), the description is fairly complete. It explains the return style (aggregate counts, compact totals, optional item-level rows), the intersection behavior, and the strict output verification rules. It does not detail error conditions or edge cases, but the provided information is sufficient for an agent to select and invoke the tool correctly.

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 description coverage is 73%, so the baseline is 3. The description adds context for the ending-window and watchers intersection by mentioning 'listings ending within the requested window that also have watchers,' which helps understand combinations like ending_within_days + watchers_only. However, it does not explain the undocumented parameters (max_pages, page_size, matching_listing_limit) beyond the schema, so it doesn't fully compensate for the coverage gap.

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 opens with a specific verb+resource: 'Return aggregate counts for the authenticated seller active GunBroker listings.' It clearly distinguishes from raw listing pages by stating 'returns compact totals instead of raw listing pages,' which differentiates it from sibling tools like list_gunbroker_items_selling. The purpose is unambiguous.

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?

The description implies when to use the tool: when aggregate counts or compact totals are needed, contrasting with 'raw listing pages.' It does not explicitly name sibling tools or provide 'when-not-to-use' exclusions, but the context is clear enough. The 'Data accuracy contract' also instructs how to handle the tool's output, which aids in correct usage.

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