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

Annotations already declare readOnly/openWorld/idempotent/non-destructive. Description adds value by disclosing that card terms change and vary by market, that figures are verified against issuer, and that VoyageHacks may earn a commission. These are behavioral/commercial details an agent cannot infer from annotations or schema.

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?

The description is front-loaded with the primary action, then moves through usage triggers, exclusions, caveats, and disclosure. Every sentence earns its place; there is no redundant or vague wording.

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?

The tool has three optional, fully documented parameters and an output schema, so return-value details are covered elsewhere. The description supplies everything else: scope, limitations, data freshness, attribution requirement, and referral disclosure, making it complete for agent selection and invocation.

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 parameters are already well documented. The description adds context about card availability and country orientation but does not need to repeat parameter semantics. Baseline 3 is appropriate because the schema carries 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?

The description opens with a specific verb and resource: 'Return American Express application links...' and enumerates exactly what is included (cards, fee/welcome-offer figures, up to four guides). It clearly delimits itself from sibling tools by stating 'It covers American Express only' and listing what it does not do.

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?

The description gives explicit trigger conditions: 'Useful when a user asks about travel rewards, points, miles, lounge access, which card to pay with abroad or foreign-transaction fees.' It also states exclusions – no eligibility decision, approval, credit-score check, or application – so an agent knows when not to invoke it for comparison or eligibility queries.

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