gtin_check_digitCompute the mod-10 check digit for GTIN/EAN/UPC data digits (all digits EXCEPT the check digit). Use to generate or repair a barcode.
| Name | Required | Description | Default |
|---|---|---|---|
| data | Yes | The data digits without the check digit, e.g. "400638133393". |
Changes observed during successful MCP inspections.
Input schema / examplesAdded value: +[
+ {
+ "data": "400638133393"
+ },
+ {
+ "data": "003600029145"
+ }
+]Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint, idempotentHint, destructiveHint, so safety and idempotency are clear. The description adds minimal behavioral context beyond the algorithm (mod-10). No contradictions.
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 core action, no wasted words. Efficient and clear.
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 simple computational tool with one parameter and rich annotations, the description covers purpose and usage. It could mention the return value format, but is 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?
Schema coverage is 100% with a clear description of the 'data' parameter. The description reinforces that it should be digits except check digit, but adds little 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 computes the mod-10 check digit for GTIN/EAN/UPC data digits, excluding the check digit itself. It distinguishes from the sibling tool 'validate_gtin' which validates the full GTIN.
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 says 'Use to generate or repair a barcode,' providing clear context. It does not explicitly list when not to use, but the sibling tools imply alternatives.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
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