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

With no annotations provided, the description carries the full burden of behavioral disclosure. It states the core behavior and includes a useful caveat: 'when recognizable' regarding version and variant reporting, indicating that the tool may not always be able to determine these. However, it does not disclose the return format (e.g., boolean, object) or edge-case handling (e.g., nil UUID), which leaves some ambiguity. Still, the provided behavioral context is honest and non-misleading, warranting a score above 3.

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 compact and highly structured. The opening sentence states the core purpose, followed by concise bullet-point lists for use and non-use cases. Every sentence serves a purpose, with no unnecessary elaboration or repetition. It is front-loaded and immediately actionable, ideal for an agent scanning tool descriptions.

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?

This is a simple single-parameter validation tool with no output schema. The description covers the tool's purpose, usage scenarios, and exclusions, which is largely complete. The main gap is the lack of explicit return-value details (e.g., does it return a simple boolean or an object with version/variant?). However, given the tool's low complexity and the richness of the rest of the description, it is adequately complete for effective selection and invocation.

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% coverage for the single parameter 'value' with description 'UUID candidate string'. The description adds general context about well-formedness and version/variant but does not specify format details such as case sensitivity or canonical form beyond what the schema implies. Given the high schema coverage, the description's marginal contribution is sufficient for a baseline score of 3.

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 opens with a specific action: 'Check whether a string is a well-formed UUID and, when recognizable, report its version and variant.' This clearly identifies the resource (UUID strings) and the operations (validation + version/variant reporting). It also implicitly distinguishes itself from sibling validation tools like isbn_validate and json_validate by the explicit exclusions in the 'Do not use when' section.

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 includes dedicated 'Use when' and 'Do not use when' sections. The 'Use when' section gives concrete example questions and contexts (validating a UUID before using it as a primary key). The 'Do not use when' section explicitly names alternatives (isbn_validate, json_validate) and states when generation is not appropriate. This is exactly the level of guidance expected.

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