Validate Luhn check digits for credit cards, IMEI numbers, and similar identifiers, or generate the correct check digit from a partial number.
Validate or generate a Luhn check digit (credit cards, IMEI, etc.).
| Name | Required | Description | Default |
|---|---|---|---|
| mode | No | 'validate' (default) or 'generate' to compute check digit. | |
| number | Yes | Digit string to validate or partial number for generation. |
Changes observed during successful MCP inspections.
v0.1.11Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are present, so the description carries the full disclosure burden. It never says what is returned (boolean vs check digit), how invalid input is handled, whether length/format constraints apply, or that generate mode consumes a partial number. The domain examples are context, not behavior.
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?
A single front-loaded sentence with no filler; the parenthetical examples earn their place and nothing is wasted.
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?
For a two-parameter tool with a fully documented schema and no output schema or annotations, the description is adequate on purpose but leaves the generate-mode return value and error behavior unexplained, which an agent would need in order to use the output correctly.
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 100%, so both 'mode' and 'number' are already documented in the schema, establishing the baseline of 3. The description adds no syntax, format, or length details for the number string beyond repeating usage context.
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?
States a specific verb (validate/generate) and resource (Luhn check digit) with concrete examples (credit cards, IMEI). It is unambiguous what the tool does, though the dual validate/generate purpose sits slightly awkwardly against a name that says only 'validate'.
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?
No guidance on when to choose this tool, no prerequisites, and no explanation of when to pick 'validate' vs 'generate' beyond the mode parameter's own schema text. The reader must infer the two modes' use cases entirely.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.