update_card

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

With no annotations provided, the description carries the full burden. It successfully discloses the delayed effect ('Changes take effect after issuer confirms'), but omits other key behaviors such as idempotency semantics (despite the client_request_id parameter), partial vs. full update semantics, or error handling when issuer confirmation fails.

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 optimally concise with two efficient sentences. The first establishes purpose and scope; the second provides operational constraints and behavioral expectations. Every clause conveys necessary information without redundancy.

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 lack of annotations and output schema, the description provides minimum viable coverage for a financial mutation tool. It identifies the async confirmation behavior but should explicitly confirm this performs partial updates (PATCH semantics) and describe the idempotency behavior implied by client_request_id.

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?

While the schema has 100% coverage (baseline 3), the description adds valuable cross-parameter semantics: the constraint 'At least one field must be provided' clarifies that despite only card_id and client_request_id being marked required, the caller must provide at least one of tx_limit, allowed_mcc, or blocked_mcc.

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 specific action ('Update') and domain ('card risk controls'), distinguishing it from siblings like refill_card (balance) or create_card_order (issuance). It explicitly identifies the configurable resources: 'per-transaction limit and MCC whitelist/blacklist.'

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 provides the critical operational constraint 'At least one field must be provided,' preventing empty update calls. However, it lacks explicit guidance on when to use this tool versus alternatives (e.g., when to whitelist vs. blacklist) or prerequisites like required permissions.

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