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

With no annotations, the description carries the full burden and does deliver real behavioral detail: the period is compared against 'the same length of time just before it,' Classic and UGC Limiteds are broken out separately, free claims are defined as zero-Robux, and item-for-item trades are explicitly excluded. It omits auth/permission needs, pagination, and any error behavior, keeping it below a 5.

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 and the three sentences each carry information (metrics, use cases, scoping, exclusion) with little filler. The opening sentence is dense and slightly run-on, but overall it is appropriately sized.

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 two-parameter read tool with no output schema, the description defines what is measured, the comparison baseline, and the scope exclusions, which is nearly enough to call it correctly. It does not describe the response shape (e.g., how Classic vs UGC results are returned) or auth requirements, so a small gap remains.

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 100% and both parameters are documented with their own semantics (including the enum meaning for days=9999), so the schema already does the heavy lifting. The description only restates creator_id scoping ('Pass creator_id for one creator's items') and adds nothing about the days enum, matching the baseline 3 for high coverage.

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 verb+resource (marketplace sales/free claims over a period) and enumerates the exact metrics returned (distinct items sold, copies sold, Robux spent, free claims), which lets an agent know what it produces. However, it never differentiates itself from close siblings like get_market_stats, get_market_cap, or get_community_market_history, so the 5-tier bar for sibling distinction is not met.

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 names three use cases ('how much was spent, whether the market is busier than before, or how many free UGC copies were claimed') and tells the agent when to scope with creator_id. It is clear context, but no alternative tool is named and no when-not condition is given, so it stops short of a 5.

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