validate_card

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

With no annotations, the description discloses key behaviors: verifies Luhn, detects brand from BIN, checks length, and states what it does not check. Does not describe output format or error handling, but for a validation tool the behavior is well communicated.

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, front-loaded with usage instruction, no wasted words. Efficient and to the point.

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?

Missing description of return value or output format (no output schema). For a validation tool, agents may need to know what the tool returns (e.g., boolean or result object). Otherwise, the description is specific and complete for its purpose.

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% with the 'number' parameter description already covering spaces/dashes ignored. The description adds context on what validation is performed, but does not add new parameter-specific details 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 checks payment card number structure, verifies Luhn checksum, detects brand from BIN, and checks length. It distinguishes from other validation tools by specifying card-specific checks and what it does not do (real/active/funds).

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 instructs to use this tool for checking card structure before use, and warns against assuming validity or guessing brand. It also clarifies what the tool does not check. No alternatives explicitly named, but sibling context makes this clear.

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