inventory_stats

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

The description adds context beyond the readOnlyHint annotation by noting the tool is efficient ('cheap') and does not scan items, which suggests a precomputed or optimized behavior. It also discloses the types of returned data (counts, values, time series), though it does not detail response structure or potential limitations.

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 front-loaded with a clear summary and uses a logical bulleted list for the `by` modes. Every sentence contributes necessary detail; no redundant or filler content is present, and the structure makes scanning easy.

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 no output schema, the description adequately describes the return categories (counts, total value per location/tag, value over time) and parameter usage. It does not specify the exact response shape, but for a statistics tool this level of detail is sufficient, especially with the readOnlyHint annotation.

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?

With zero schema description coverage, the description fully compensates by explaining each `by` enum value and clarifying that start/end are optional date parameters in YYYY-MM-DD format for the purchase-price mode. This provides essential meaning beyond the bare property names.

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 clearly states it provides inventory statistics for determining inventory worth, with a specific verb and resource. It distinguishes itself from siblings by focusing on aggregated value and counts rather than item-level operations, and the breakdown of `by` modes further clarifies its purpose.

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 explicitly positions this as the 'cheap way' to answer valuation questions without scanning items, implying use for aggregate analytics rather than item searches. The enumerated `by` modes provide concrete scenarios (totals, locations, tags, purchase-price), but it does not explicitly name alternative tools for item-level queries or exclusions.

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