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

Annotations already declare readOnly/idempotent/closed-world, and the description goes beyond them by disclosing the default 90-day window, the row semantics (change points, not daily samples), the currency/FX payload, and error behavior for an unknown id. Missing only things like ordering or row-count limits.

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?

Three tight sentences with the resource and window front-loaded, then the row semantics, then the error case. No filler or repetition of the title.

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 no output schema, the description carries return-shape disclosure and does it well by explaining what each row represents plus the error object. Ordering of rows and any result-size limits are the only notable omissions.

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% and already documents days (1–3650, default 90) and sku_id's origin in search_skus, so the description mainly restates the default. Its only added value is tying days to a look-back window interpretation of the returned change points.

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 resource (price change points of a SKU) and scope (last N days), and the clarification 'rows are change points, not daily samples' implicitly separates it from get_price/get_index. It never names a sibling, so an agent must infer the routing rather than read it.

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 the change-point framing, and the schema links sku_id to search_skus, but the description gives no explicit 'use this instead of get_price when...' guidance or exclusions. An agent can guess when to call it, but nothing is stated.

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