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

Annotations already declare readOnlyHint and openWorldHint, and the description adds real context beyond them: the data is voluntary and shows association rather than causation, the source is openFDA, it is not medical advice, and it discloses the x402 pay-per-call model with the fact that failed calls are not charged. It does not describe pagination or return shape, but an output schema exists to carry that.

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?

Front-loaded with the core value proposition, then caveats, source, disclaimer, and pricing in a compact multi-clause sentence. Most clauses earn their place, though the pricing/disclaimer tail is slightly dense.

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 annotations covering the safety profile and an output schema carrying the return shape, the description supplies the remaining essentials: source, data reliability caveat, and cost. Complete for a simple two-parameter lookup, with only minor gaps around result handling.

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 parameters (drug, limit) are already documented in the schema. The description adds no syntax, format, or constraint details beyond it, making the baseline 3 correct.

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+resource: returns the most reported adverse reactions to a drug from FDA's FAERS database, with explicit output contents (counts, total reports, serious share). The FAERS framing clearly separates it from adjacent siblings like fda_label or clinical_trials.

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 by the data caveat (voluntary reports, association not causation), which hints this is for signal detection, but there is no explicit when-to-use or when-not-to-use guidance and no named alternative sibling. A reasonable but not directive set of guidelines.

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