Detect Card Type

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

With no annotations provided, the description carries the full burden. It discloses the core behavior (uses the IIN/BIN prefix) and the input requirement (digits only, caller must strip spaces/dashes). However, it does not describe what happens for invalid inputs (e.g., unknown prefix, out-of-specified length) or clarify that it performs no validation (suggested by sibling). There is no mention of side effects, but none are expected. It provides some transparency but leaves gaps.

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 two concise sentences that pack essential information: purpose, network list, and input preprocessing instruction. There is no extraneous text. It front-loads the core action and follows with important input guidance. 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?

The tool is simple with one parameter and an output schema, so description need not explain return values. It covers purpose, input format, and the IIN/BIN mechanism. It lacks explicit caveats (e.g., handling of unknown networks, validation not performed) but given complexity and annotations, it is reasonably complete. The lack of usage guidance vs. siblings is a minor gap, but overall adequate.

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 description adds value beyond the schema: it clarifies the parameter is the full card number and explicitly states that spaces/dashes should be removed, which complements the pattern '^\d{8,19}$'. It also explains the number's use (IIN/BIN prefix) that the schema doesn't convey. However, it does not mention the parameter name by name or provide additional format details (e.g., maximum length, examples). Given the schema has strong constraints, the description provides marginal extra semantics but not complete coverage.

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 function: 'Identifies the card network (Visa, Mastercard, American Express, Discover, Diners Club, JCB) from the card number's IIN/BIN prefix.' It specifies the resource (card number) and the action (detect card type), and lists the distinct networks. This distinguishes it from siblings like 'validate_card_number' (validation) and 'validate_iban' (IBAN), making the purpose unambiguous.

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 notes an input precondition: 'Accepts digits only (spaces/dashes should be stripped by the caller).' This is a clear usage instruction on formatting, but it does not provide guidance on when to choose this tool versus the sibling tools (validate_card_number, validate_iban). The usage is implied by the tool's name and purpose, but no explicit alternatives or exclusions are given. As such, it is adequate but not explicit.

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