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

Annotations only cover readOnly/openWorld, but the description adds the operationally decisive context an agent needs before spending money: a hard cap of 10 applications per call and a $0.002 USDC charge per successful call via x402 on Base, Solana or Arc, with failed calls not billed. Cost, payment rails and billing failure semantics are exactly the traits annotations cannot convey.

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 sentences, no filler: resource and filter first, then limits and price. Each clause carries distinct information (source, key, returned fields, cap, cost, billing exception) with nothing repeated from 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 an output schema present, return-field details are technically redundant but harmless, and the pricing/limit coverage makes the definition self-sufficient for invocation. Minor gap: no note on how partial or zero matches behave (e.g. ingredient not found, brand-name input rejected), which matters for a paid per-call tool.

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% — both 'ingredient' (letters/spaces, 2-60 chars) and 'max' (1-10, default 5) are fully documented in the schema. The description reinforces the ingredient key and the 10-per-call ceiling but adds no format or matching nuance beyond that, so the baseline 3 applies.

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 names a specific source (FDA Drugs@FDA / openFDA) and a specific filter key (active ingredient), then enumerates the returned fields (application number, sponsor, brand names, dosage form, marketing status, TE code). That is enough for an agent to distinguish it from adjacent drug tools, though it never explicitly contrasts itself with siblings like health_fda_purple_book or health_drugbank_interaction.

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 only implied by the phrase 'by active ingredient' — there is no explicit statement of when to choose this over the other FDA/EMA/drug-reference siblings, nor any exclusion or prerequisite (e.g. exact ingredient spelling, generic vs brand). An agent must infer the routing decision itself.

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