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

Annotations already declare readOnlyHint and openWorldHint, but the description adds genuinely non-obvious behavior: a $0.002 USDC per-call cost, the exact failure mode when unpaid, and the three ways to supply payment. It also draws a scope boundary ('No patient records or medical advice'). It does not describe result shape or pagination/count behavior, which keeps it from a 5.

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 purpose, then scope exclusion, then payment mechanics. The payment sentence is dense but every clause is actionable for a caller. Minor cost: the header/param enumeration is long for a description and could partly live elsewhere.

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?

For a read-only search tool with no output schema, the description covers purpose, category scope, exclusions and the full paid-call handshake, which is the main failure mode an agent would hit. The one real gap is that it never characterizes the response content (recall records, fields, total counts) beyond the unpaid error case.

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 query, category and limit are already documented with types, defaults, enums and length bounds; that sets the baseline at 3. The description adds only a loose hint that classification, status and dates are searchable, which is not mapped to any parameter and could mislead an agent into expecting fields that don't exist in the schema.

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 official FDA food, drug or device enforcement recalls') and enumerates the searchable dimensions (product, classification, status, dates). This clearly separates it from sibling recall tools like us_cpsc_recalls and vehicle_recalls without needing to name them.

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?

Gives a clear usage context (FDA enforcement recalls across food/drug/device) plus an explicit operational procedure for the paid call: first call returns x402 requirements, retry with X-PAYMENT or PAYMENT-SIGNATURE header. It does not explicitly say when to prefer us_cpsc_recalls or vehicle_recalls instead, so alternative routing is left implicit.

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