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

Annotations already cover the read-only and non-destructive nature, so the description only needs to add behavioral context. It does so by disclosing that the result is an observed series over time with observation dates and current product attributes, plus marketplace and single-ASIN limits. It stops short of detailing the exact history window or data granularity, but annotations lower the burden.

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 the core definition, followed by trigger examples, sibling routing, and constraints. Every sentence earns its place and there is no fluff or repetition. Despite being longer than average, all content contributes directly to correct tool selection and invocation.

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 read-only single-resource tool with no output schema, the description covers the main return contents, usage scenarios, sibling alternatives, and invocation constraints. Minor details like the length of history or number of data points are omitted, but an agent has enough information to select and call the tool correctly in most situations.

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%, so the schema already documents asin and marketplace_id fully. The description reinforces 'one ASIN per call' and 'Amazon marketplaces only' but does not add meaningful parameter-level semantics beyond what the schema provides. A baseline of 3 is appropriate.

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 precise statement of what the tool does: returns the BSR history time series for one Amazon ASIN, including first/last observation dates and product identity fields. It is clearly differentiated from the closest sibling tools by name and behavior, so an agent can select it correctly without checking other schemas.

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 states when to use the tool: when the user asks how an ASIN's rank/demand has moved, with concrete example queries. It also names the alternatives for related but different needs, asin_buybox_history and collect_asin_now, and adds constraints like Amazon marketplaces only and one ASIN per call.

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