Validate GTIN-8, UPC/GTIN-12, EAN/GTIN-13 and GTIN-14 check digits; no product lookup. FREE during validation. No key, credits, wallet or preparation needed. Supply your task in input. Existing source and input limits apply.
| Name | Required | Description | Default |
|---|---|---|---|
| input | Yes |
| Name | Required | Description | Default |
|---|---|---|---|
| scope | Yes | ||
| valid | Yes | ||
| format | Yes | ||
| expectedCheckDigit | Yes |
Changes observed during successful MCP inspections.
Input schema / properties / maxPriceMicroUsdRemoved value: -{
- "description": "Optional legacy field; ignored in free mode.",
- "minimum": 0,
- "type": "integer"
-}Input schema / properties / requestIdRemoved value: -{
- "description": "Optional legacy field; ignored in free mode.",
- "type": "string"
-}Input schema / properties / maxPriceMicroUsd / descriptionPrevious value: -"Explicit maximum new debit; 0 means recovery only."New value: +"Optional legacy field; ignored in free mode."Input schema / properties / maxPriceMicroUsd / maximumRemoved value: -999999999999Input schema / properties / requestId / descriptionPrevious value: -"Persist the ID returned by agent_utilities_prepare. Reuse after uncertainty."New value: +"Optional legacy field; ignored in free mode."Input schema / properties / requestId / patternRemoved value: -"^\\d{13}_[A-Za-z0-9_-]{16,80}$"Input schema / requiredPrevious value: -[
- "input",
- "requestId",
- "maxPriceMicroUsd"
-]New value: +[
+ "input"
+]Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare the read-only, non-destructive, closed-world profile. The description adds genuinely useful context beyond them: pricing ('FREE during validation'), auth requirements ('no key, credits, wallet'), and a rate/limit caveat ('existing source and input limits apply').
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?
Front-loaded with the useful content (formats + no-lookup scope), but several sentences are boilerplate ('Supply your task in input', 'Existing source and input limits apply') that add little and one is mildly confusing about what 'task' means.
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?
With an output schema present, return values need no explanation, and annotations carry the safety profile. Still, for a tool with a nested required object and 0% schema coverage, the description leaves the input shape unclarified, which is a real 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% and the single nested parameter (input.code, maxLength 32) is undocumented. 'Supply your task in input' is boilerplate that does not tell the agent that input.code should hold the GTIN string, so it fails to compensate for the coverage gap.
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) and resource (GTIN-8/UPC-12/EAN-13/GTIN-14 check digits), and explicitly scopes it with 'no product lookup', which cleanly distinguishes it from siblings like commerce_main_product and commerce_offer_extract.
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?
Implies usage well (pure check-digit validation, not a product lookup) and notes it is free with no key/credits/wallet required. However, it never names an alternative tool or states an explicit when-to-use vs when-not condition, leaving routing to inference.
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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