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

Annotations already carry readOnly/openWorld/idempotent/non-destructive hints, so the bar is lower. The description adds genuine value beyond them: 'Keyless' discloses auth requirements (none), and the field inventory tells the agent the record includes market status with original marketing date, enabling date-sensitive questions. It does not cover error behavior for unknown identifiers, but nothing contradicts 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?

Four sentences with no filler: content fields first, then capability examples, then invocation syntax, then auth. The example calls are concrete and the 'Keyless' tag is economical. It is on the longer side, and the question examples in sentence two partially overlap the field list in sentence one, but each sentence earns its place.

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 correctly shoulders the burden of describing return content, and it does so thoroughly (brand name, DIN, company, every active ingredient with strength, dosage form, route, market status, marketing date). Identification methods, invocation examples, and auth are all covered. Minor gaps remain for edge cases, such as behavior when both identifiers are supplied or the product is not found, but nothing critical is missing for a simple two-parameter lookup.

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% — both din and drug_code are already documented with format details ('8 digits, leading zeros matter', 'Health Canada internal drug code'). The description's phrase 'by its DIN or by the Health Canada drug code' clarifies that the two parameters are alternative identifiers, slightly reinforcing what the schema examples already imply, but it adds no new semantic detail.

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 'Full Health Canada record for one Canadian drug product' — a specific retrieval scope with a concrete field inventory (brand name, DIN, company, ingredients, strength, dosage form, route, market status). It distinguishes itself from the sibling search/list tools by emphasizing 'one' product and by framing its lookup keys (DIN or drug code), and the example questions ('what is in this Canadian drug', 'is this product still marketed') make the operation unmistakable.

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 clear usage context: use this when you have a DIN or Health Canada drug code and need the full record for a single product. It does not explicitly name alternatives or state when not to use it, despite the closely related siblings health_canada_search_drugs and health_canada_drugs_by_ingredient — a missed routing opportunity, but the context is clear enough that an agent can infer when this detail tool applies.

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