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

Annotations already declare non-read-only, idempotent, non-destructive, closed-world, so the safety profile is covered. The description adds useful context (Ed25519 type, JWS proof purpose, rotation behavior) but omits whether authentication is required, what happens to a previously registered key on rotation, and what an invalid key produces.

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?

A single front-loaded sentence with no filler; the operation and its purpose appear immediately. Nothing extraneous and nothing buried.

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 one-parameter registration/rotation tool with annotations covering safety and no output schema, the essentials are present. Gaps remain around authentication requirements, key format, and the effect of rotation on existing keys, which an agent would need before calling confidently.

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 coverage is 0% for the single parameter, so the description must compensate. Naming 'Ed25519' narrows the expected key type, but the encoding/format of public_key (raw base64, PEM, hex) and any length constraints remain undocumented in both schema and description.

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 pair ('attach or rotate') and a specific resource ('Ed25519 public key'), which is concrete enough for an agent to know exactly what the call does. It stops short of differentiating from the nearest sibling, rotate_secret, which also performs rotation semantics.

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?

'For optional JWS proof signatures' hints at the purpose but never states when an agent should call this versus rotate_secret or sign_up. The word 'optional' implies the feature is not mandatory, but no prerequisite or exclusion is spelled out.

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