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

Annotations already mark the tool read-only, idempotent, open-world, and non-destructive, so the description correctly focuses on additional behavior: one row per published week, oldest-to-newest ordering, pricing unit, percentage change across the window, and 'Keyless'. This adds useful context beyond the annotations.

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 sentences, each earning its place: purpose/scope, usage signals, and return behavior. The most identifying information is front-loaded, and the final 'Keyless' note is compact and useful.

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 simple two-parameter read tool with no output schema, the description adequately covers input scope, intended use, return row structure, and ordering. It is complete enough to call correctly, though the exact meaning of 'percentage change across the window' is slightly ambiguous.

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%, with both ndc and weeks clearly documented in the input schema. The description adds no new parameter-level meaning beyond restating 'one drug NDC' and weekly observations, so the baseline of 3 applies.

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 'Weekly price history for one drug NDC' — a specific verb and resource — and immediately clarifies it tracks NADAC pharmacy acquisition cost over time. It also names concrete use cases, making it easy to distinguish from a current-price tool like nadac_price.

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 gives explicit usage signals: 'has the price of this generic gone up', 'shortage-driven price spikes', and 'generic erosion after a patent expiry'. It does not explicitly name alternatives or state when not to use it, but the use cases are specific enough for an agent to route correctly.

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