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

Annotations already declare readOnlyHint, idempotentHint, and openWorldHint=false, so the safety profile is covered structurally. The description's added value is naming the payload: per-source provenance plus cross-source identifiers, which is genuinely useful given there is no output schema. It says nothing about behavior on a missing or invalid id, so it adds partial rather than rich context.

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?

One compact sentence with the action and the returned payload front-loaded; the parenthetical identifier list is dense but informative. No filler, though the "+" shorthand is slightly terse for formal documentation.

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 one-parameter read tool with no output schema, the description covers the important unknown — what comes back (provenance and cross-source IDs). Only the not-found/error behavior is unaddressed, which is a minor gap at this complexity.

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 0% for the single integer parameter, so the description carries the burden. Saying "by id" and "canonical drug product" signals that the id is the canonical drug-product identifier rather than an NDC or RxCUI, which is a real clarification. It still does not state id origin or what an unknown id yields.

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 and resource with scope: "Fetch one canonical drug product by id." The phrase "one ... by id" implicitly separates it from the sibling drugs_search, which returns many. It stops short of naming the sibling explicitly, so it is clear but not maximally differentiating.

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 "by id" framing implies this is the follow-up lookup after a search, but the description never states when to prefer this over drugs_search or that an id must first be obtained elsewhere. Usage is inferable rather than stated.

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