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

Annotations already declare readOnlyHint=true and destructiveHint=false, covering the safety profile. The description adds useful content disclosure (returns saved credit/debit cards with payment IDs) but says nothing about auth requirements or behavior when no methods are saved; with annotations doing the heavy lifting, this is adequate rather than rich.

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 short sentences, front-loaded with the verb and resource, and the second sentence earns its place by naming the return payload and the downstream tool.

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?

Zero params, annotations covering safety, and an output schema present mean little else is required; the description supplies the one thing structured fields cannot, the reason to call it (to obtain payment IDs for book_hotel). It could note the no-results case, keeping it just below 5.

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 takes zero parameters, so the schema-based baseline of 4 applies; there is no parameter surface the description could or should explain.

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 ('List') and resource ('user's saved payment methods') with the purpose (booking), which cleanly separates it from read-only siblings like get_loyalty_accounts or get_travel_profiles that also list user data.

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 ties usage to booking and names the dependent tool ('needed for the book_hotel tool'), so an agent knows this is a prerequisite step. It does not state exclusions or alternatives (e.g., when payment IDs are not required), so it falls short of a 5.

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