Katzilla MCP

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

Annotations already indicate read-only, non-destructive, idempotent, and open-world behavior. The description adds valuable context beyond annotations: it specifies the data source (Binlist Free API), update frequency (monthly), and details about the return format (Katzilla envelope with quality scores and citation). This enriches the agent's understanding without contradicting 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 efficiently structured in two sentences: the first states the purpose and source, and the second explains the return format and its components. Every sentence adds essential information without redundancy, making it front-loaded and concise.

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 tool's simplicity (one parameter, high schema coverage, annotations provided, and an output schema exists), the description is complete. It covers purpose, source, update frequency, and return format, which is sufficient for an agent to understand and use the tool effectively without needing to explain return values (handled by output schema).

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% description coverage, with the 'bin' parameter clearly documented as 'Bank Identification Number (first 6-8 digits of card)'. The description does not add any additional semantic details about the parameter beyond what the schema provides, such as validation rules or examples. Thus, it meets the baseline for high schema 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 purpose: 'Look up card BIN/IIN information (bank, type, brand, country)' with a specific verb ('look up') and resource ('card BIN/IIN information'). It distinguishes itself from siblings by specifying its unique data source (Binlist) and return format (Katzilla envelope), making it highly specific and differentiated.

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 clear context for when to use this tool: for looking up card BIN/IIN information. It mentions the source (Binlist Free API) and update frequency (monthly), which helps set expectations. However, it does not explicitly state when not to use it or name alternative tools for similar purposes, such as other financial lookup tools that might exist among siblings.

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