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

With no annotations provided, the description carries the full behavioral disclosure burden. It explicitly discloses the override effect (allows a charge that would be denied), indicates persistence through 'remember,' and clarifies scope by stating it does not replace the preset. It omits details like how to undo the action or whether the allowance expires, but the core behavior is transparent.

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 consists of two concise sentences that front-load the core purpose and include a useful scope caveat. There is no fluff, and every word earns its place.

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 simple 2-parameter tool with an output schema, the description is mostly adequate, but it does not address the notable fact that card_id is not required while the description says 'on a card.' It also leaves merchant matching semantics unspecified. Sibling buy_unlink_merchant suggests an undo path exists, which the description could have noted for completeness.

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% for both parameters, so the baseline is 3. The description adds contextual meaning by linking the pattern to merchant matching, but it does not clarify the optionality of card_id or the exact matching semantics (case sensitivity, exact vs. substring). The description adds no significant information beyond the 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?

The description clearly states the tool's specific action: remembering a merchant on a card so that the next matching charge is allowed even when card category or merchant rules would deny it. This distinguishes it from sibling tools like buy_unlink_merchant (which presumably removes such an exception) and set_card_preset (which manages broader preset rules).

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 implies when to use this tool (to allow a specific merchant charge that would otherwise be denied) and includes the scope note 'does not replace the rest of the preset.' However, it does not explicitly name alternative tools or state when not to use it, leaving the guidance mostly implied rather than actionable.

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