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

Annotations only declare readOnlyHint=true, so the safety profile is already carried by structured data. The description adds the backing endpoint ('openFDA drug/ndc endpoint'), which is mild context, but says nothing about pagination ceilings (the schema does), rate limits, or API-key requirements that openFDA callers should expect.

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?

Two tightly packed sentences, front-loaded with the resource and scope; the endpoint clause is the only marginal extra. No filler, no restatement 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 usefully doubles as a return-value summary by enumerating the product attributes returned. Combined with 100% schema coverage and a readOnly annotation, the definition is close to complete; only guidance on alternatives and API constraints is absent.

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 skip/limit/sort/search are fully documented in the schema itself. The description's field list gives a hint about which fields the Lucene query can target, but adds no query syntax or parameter detail beyond what the schema already provides.

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 ('Search the National Drug Code (NDC) directory') and enumerates the content scope (code, name, dosage form, route, ingredients, marketing status, labeler). This field list implicitly separates it from siblings like search_drug_labels or search_drug_events, though it never explicitly contrasts them, so it stops short of a 5.

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 rather than stated: an agent can infer this is the tool for product/code-level lookup because the enumerated fields are all NDC product attributes. There is no explicit when-to-use, no exclusions, and no mention of which sibling to prefer for label text, adverse events, or recalls.

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