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

Annotations already declare destructiveHint=true and idempotentHint=true; the description adds the specific destructive mechanism (full-list replacement, not append/merge), which annotations alone don't convey. It stops short of saying what happens to cards whose required membership is dropped, or how unknown values are handled, but the main risk is disclosed.

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 sentences, zero filler. The purpose comes first and the replacement warning follows immediately, so the most consequential instruction is front-loaded rather than buried.

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?

With an output schema present and a single fully-described enum parameter, the description needn't explain return values. It covers purpose and replacement semantics well; only edge behavior (invalid values, effect on dependent card rate calculations) is left unstated, which is a modest gap for this complexity.

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 coverage is 100% and the enum plus its description already enumerate the allowed values, so baseline is 3. The description adds genuine meaning beyond the schema by explaining what a membership does (unlocks elevated card rates) and tying an example value to a concrete card benefit, which helps the agent populate the array correctly.

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 ('sets') and resource ('memberships') and immediately grounds it in effect: memberships that unlock some cards' rates, with two concrete examples (amazon-prime for Prime Visa's 5%, BofA Preferred Rewards tier). No sibling tool touches memberships, so the scope is unambiguous.

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 warns that the call replaces the whole list and instructs the agent to include the ones to keep — a critical precondition that prevents accidental data loss. It does not name alternatives, but no sibling overlaps with this resource, so the omission costs little.

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