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

Annotations already declare readOnlyHint=true and destructiveHint=false. The description adds behavioral context beyond that by explaining the result's interpretive value ('tells the user whether they can decline the rental company's expensive insurance') and confirming this is a non-mutating lookup. No contradiction with annotations.

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 with no filler. Purpose is front-loaded, the use case is explained in a compact aside, and the parameter guidance is condensed into one clear either/or sentence. Every sentence earns its place.

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, timing, parameter alternatives, and result interpretation, and the output schema covers return structure so it need not be repeated. Minor gap: it doesn't explicitly distinguish itself from the sibling get_vehicle_booking_coverage tool, though the credit-card framing makes confusion unlikely.

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?

The schema already documents all three parameters with 100% coverage, so the baseline is 3. The description adds meaningful semantics beyond the schema: it specifies the exclusive either/or relationship between credit_card_product_name and card_number_bin + card_provider, and explains that the BIN path is network-tier-based while the product name path is exact-match.

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 lookup operation ('Look up rental car CDW/LDW coverage'), names the exact resource (credit card coverage), and ties it to a concrete decision (declining rental company insurance). It is clearly differentiated from sibling booking-coverage tools by focusing on credit-card-provided coverage rather than booking-level coverage.

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?

Explicitly frames when the tool is useful ('before booking') and gives clear either/or parameter guidance for invocation. However, it does not explicitly name alternatives or exclusion conditions, such as when get_vehicle_booking_coverage would be more appropriate.

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