mercury_list_cards

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

Annotations already indicate readOnlyHint=true, confirming no side effects. The description adds value by specifying the return format (cards array with fields like id, last4, type) and noting current API limitations (no card creation/freezing), which goes 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?

The description is concise (4 sentences), well-structured with clear sections (USE WHEN, DO NOT USE, RETURNS), and contains no redundant information.

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 low complexity (single parameter, no output schema), the description covers the purpose, usage guidelines, return format, and limitations completely. No additional information is needed for an agent to correctly select and invoke the tool.

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 input schema has 100% coverage for the single parameter accountId, which is clearly documented. The description does not add further semantic meaning beyond the schema, but the schema itself is sufficient.

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 explicitly states it lists physical and virtual cards attached to a Mercury account, with a specific verb and resource. It distinguishes from sibling tools like mercury_list_credit_transactions by exclusion, ensuring no ambiguity.

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?

Clear 'USE WHEN' and 'DO NOT USE' sections provide explicit context for when to use this tool (e.g., spend audits, freezing review) and when not to (e.g., listing credit transactions, which points to an alternative sibling). Also notes API limitations for card creation and freezing.

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