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

Annotations already declare idempotentHint=true and readOnlyHint=false. Description adds that the closest match is saved and echoed back, and that smart_excluded does not remove the card. It also mentions user confirmation for uncertain matches, adding behavioral context beyond 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, no filler. Purpose is front-loaded, id source mentioned, and flag behaviors succinctly covered. Every sentence adds value.

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?

For a 4-parameter tool with output schema, description covers all parameters, mentions confirmation behavior, and clarifies the smart_excluded semantics. Minor gaps like exact output structure are likely covered by the output schema.

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 covers all parameters (100%), so baseline is 3. Description enhances meaning by explaining the purpose of product, clear_product, and smart_excluded in context, and clarifies that clear_product and product should not be combined. Adds value beyond schema.

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?

Description states a clear verb ('tell the vault') and specific resource (card product for a stored card), with explicit purpose for smart purchases. It also references list_cards as the id source, distinguishing it from other card tools.

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?

Provides guidance on when to use the flags (clear_product, smart_excluded) and mentions user confirmation. Does not explicitly compare to sibling tools like recommend_card or get_card_details, but implies usage via the id source from list_cards.

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