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

Annotations already declare readOnly/idempotent/non-destructive/closed-world, so the safety profile is covered. The description adds value beyond them by disclosing the return shape ('Returns true or false') and the scope limits ('does not check uniqueness or resource existence'), which prevents misuse as an existence probe.

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 tight sentences with no filler: the core action and scope come first, then the sibling routing, then the return/limits caveat. Every clause carries 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?

No output schema exists, but the description states the boolean return, and it covers the primary misuse case (uniqueness/existence) for a simple 2-parameter validator. Nothing an agent needs to call this correctly is missing.

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 `uuid` and `version` are already documented, including the 1-8 range and omit-for-any behavior. The description's phrase 'optional RFC variant/version' adds only a light conceptual hint (variant) over the schema, so the baseline of 3 applies.

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 and resource ('Check canonical UUID syntax') plus scope qualifiers ('optional RFC variant/version'), and contrasts with the generate-token sibling. An agent can distinguish it from the many is-*-safe siblings purely from the name plus this sentence.

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 validate UUIDs; use generate-token to create them', naming the alternative tool for the inverse operation. It also sets a boundary by ruling out uniqueness and resource-existence checks, though it gives no guidance on when a different is-*-safe validator would be preferred.

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