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

No annotations are provided, so the description carries the burden. It discloses that output is masked and that the operation costs $0.002, which is useful behavioral context. However, it doesn't disclose what happens with invalid numbers, whether the tool performs network calls, or any rate limits. The price and masked output are good additions but not comprehensive.

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 a single compact sentence that packs the core purpose, output fields, and a key behavioral note (masked output, price). Every word earns its place. It's front-loaded with the primary function.

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 has an output schema, so return values are covered elsewhere. The description covers the core purpose and a cost/masking caveat. However, it lacks input format guidance and any usage context (e.g., when to use this vs other card tools). For a paid tool, the missing input format details are a notable gap.

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 description coverage is 0%, so the description must compensate. It mentions 'number' implicitly via 'BIN/IIN fingerprint' but doesn't explain the format expected (e.g., full card number vs BIN only, digits only, length constraints). The agent_id parameter is completely undocumented in both schema and description. This is a significant gap for a tool with only 2 parameters.

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 states a specific verb+resource: 'BIN/IIN fingerprint' with concrete outputs (network, expected length, Luhn validation). It clearly identifies what the tool computes. It doesn't explicitly differentiate from siblings, but the domain (card fingerprinting) is distinct enough among the listed tools.

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 usage context: it's for card BIN/IIN fingerprinting, and the masked output and price hint suggest it's a paid lookup. However, it doesn't explicitly state when to use this vs alternatives or mention any exclusions. The sibling list contains other card-related tools (ddg_checkout_conformance, ddg_seller_trust_badge), but no routing guidance is given.

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