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

Annotations cover readOnlyHint, openWorldHint, and idempotentHint, so the safety profile is already clear. The description adds important payment behavior: 'Returns the x402 payment requirements unless payment_signature is given.' This is valuable context not present in annotations. However, it doesn't describe the return format or data freshness, which is a minor gap given the read-only nature.

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 are efficient and front-loaded: the first states the purpose, the second states usage and payment behavior. The sample URL is included but doesn't detract. Could be slightly tighter by omitting the sample reference, but it's useful for developers.

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?

Covers purpose, usage, and payment mechanics, which are the key requirements for an agent to invoke this tool correctly. With no output schema, the description could say more about the response shape, but annotations and the title already indicate it returns label, recall, and adverse event data. For a read-only tool with full schema coverage and clear payment behavior, it's nearly complete.

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 are fully documented in the schema. The description adds no additional parameter syntax or format details beyond what the schema provides. Baseline 3 is appropriate when 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 specific verb and resource: checks 'official US label warnings, recalls and most-reported adverse reactions' for a medicine. The name 'drug_safety' and title match, and the specificity (label warnings, recalls, adverse reactions) clearly distinguishes it from any sibling tool, none of which deal with pharmaceuticals.

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?

Provides clear usage context: 'Use when an agent needs citable FDA facts about a drug.' This is a positive when-to-use statement, but doesn't explicitly name alternatives or exclusions. Sibling tools are all unrelated, so no exclusion is needed, but the description doesn't say when *not* to use this tool (e.g., for non-US drugs or general medical advice).

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