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

The description discloses key behavioral traits beyond the minimal annotations: the fare is charged via a hold at booking, no virtual card is created for flights, and it returns a secure checkout URL. It also clarifies what the tool does NOT do, which is important given the annotations provide no safety or side-effect information.

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 composed of three concise, information-dense sentences. It front-loads the primary purpose, then provides exclusions and an alternative, and ends with the return value. Every sentence earns its place with no redundant filler.

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?

Given the tool has no parameters but does have an output schema, the description is complete: it states the action, the specific use case, what it does not do, and the return value. It also references a sibling tool for alternative behavior, making it fully self-sufficient for an agent to select and invoke.

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 tool has zero parameters, so the baseline is 4. The description does not need to explain parameter syntax, but it adds contextual meaning about the tool's purpose and return value, which helps the agent understand the invocation context.

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 states a specific verb ('Save') and resource ('payment method') plus a clear scope: used ONLY to pay for flight bookings. It distinguishes itself from sibling tools by explicitly stating it does not fund cards or cash balance, which sets it apart from tools like add_card and add_funds.

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 usage guidance: this tool is for saving a payment method for flight bookings only. It provides an explicit exclusion ('does NOT fund cards or the cash balance') and names the alternative tool ('see add_funds'), making it clear when not to use this tool and what to use instead.

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