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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the baseline is lower, and the description still adds real information: no network access, no stored state, determinism of the input-output mapping, and concrete limits (64 KB input, 1 s per call, 1 MB result). It stops short of describing the output shape or how malformed namespaces are handled.

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 English block is front-loaded and tight, leading with the derivation and then the 'When' and 'Not for' routing. The parallel Spanish block doubles the length, which is reasonable for a bilingual server but means the text is longer than strictly necessary.

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 two-parameter, deterministic derivation tool with no side effects, the description covers what the tool computes, when to choose it, the alternative, and the operating limits. Because the input schema documents the parameters and an output schema exists, the description does not need to explain the result format.

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 the schema already documents both required parameters, and the description adds little beyond restating that a namespace and a name are hashed. It does not explain the fixed-namespace shortcuts (dns, url, oid, x500) or how a raw UUID namespace should be formatted, which would have been the genuinely useful addition.

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: derives the RFC 9562 version-3 UUID of a namespace and name using MD5. It explicitly names the sibling it is not (uuid-v5) and clarifies that the tool also decodes the fields embedded in the identifier, so an agent can distinguish it from its siblings without inspecting either schema.

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?

Uses explicit 'When' and 'Not for' clauses: use it when an identifier in this format must be generated or decoded, and not for deriving a v5 UUID (uuid-v5). It also gives a migration recommendation (RFC 9562 prefers v5) that steers an agent toward the right sibling.

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