USE THIS to verify an ISBN-13 book identifier instead of trusting that 13 digits are correct. Checks the 978/979 prefix and the mod-10 weighted check digit, and returns the expected check digit when it fails.
| Name | Required | Description | Default |
|---|---|---|---|
| isbn | Yes | The ISBN-13; hyphens and spaces are ignored. |
Changes observed during successful MCP inspections. Dates show when Glama detected each change.
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
The description discloses the validation behavior (checks prefix and check digit, returns expected check digit on failure), adding context beyond the readOnlyHint annotation. It does not mention return format or edge cases, but for a simple validation tool this is sufficient.
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 two sentences, directly front-loaded with the imperative 'USE THIS', and every phrase adds value. No extraneous information.
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 (single parameter, no output schema, read-only), the description covers key aspects: purpose, validation logic, and failure behavior. It could mention the return type, but this is not critical for a validation tool.
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 already describes the isbn parameter as 'The ISBN-13; hyphens and spaces are ignored.' with 100% coverage. The description adds no new semantic details beyond what the schema provides, meeting the baseline expectation.
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 verifies an ISBN-13 book identifier, specifying the exact checks (978/979 prefix and mod-10 check digit). It distinguishes from the sibling validate_isbn10 by explicitly mentioning ISBN-13, leaving no ambiguity about its resource.
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 explicitly advises to use this tool instead of trusting raw digits, providing a clear when-to-use directive. However, it does not mention when not to use it or directly name alternative validation tools for other formats, though the sibling list implicitly differentiates.
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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