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

Annotations already declare readOnlyHint and openWorldHint, but the description adds materially new behavioral facts: a cost of $0.002 USDC per successful call, x402 payment on Base/Solana/Arc, and that failed calls are not charged. The 'not medical advice' disclaimer further sets expectations. This is behavior an agent must know before invoking and is not derivable from structured fields.

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, front-loaded with the capability and its returned fields, then the disclaimer, then the pricing terms. Each sentence carries distinct information (capability, legal caveat, cost model) and there is no filler.

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 an output schema present, the description need not explain return structure, and annotations cover safety. The description still supplies the two things structured data lacks: the domain scope (US FDA drug listings by name) and the payment terms. Nothing an agent needs to decide to call or to invoke correctly is missing.

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 both q (2-60 chars, allowed characters) and limit (1-25, default 10) are fully documented in the schema. The description restates that searching is by brand or generic name but adds no syntax, format, or edge-case guidance beyond that. Baseline 3 is appropriate when the schema does the heavy lifting.

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 (searches) plus a precise resource (openFDA National Drug Code directory of US drug listings), and enumerates the returned fields (labeler, NDC code, dosage form, route, marketing start date, active ingredients). An agent can distinguish this from the many other registry/directory siblings without opening a schema.

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?

Clearly indicates the search axis (brand or generic name) and that the dataset is US-specific and public, which tells the agent when this tool is appropriate. It does not name alternatives such as gov_openfda_drugsfda or gov_anvisa_brazil_medicines or state exclusions, so it stops short of full when/when-not guidance.

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