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

Annotations already establish readOnlyHint=true and openWorldHint=false, so safety is largely covered. The description adds genuinely new behavioral context: the output is 128 bits of randomness and must not be treated as a secret/credential, which shapes how the agent handles the value downstream.

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 the core action first and the disambiguating caveat second. Every clause earns its place; nothing is padded or repeated from the schema.

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 zero-argument generator with annotations covering the safety profile, the definition covers what it produces and what it is not. A minor gap is the encoding/format of the returned nonce, which an agent might want before wiring it into a correlation header, though this is low risk.

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 tool takes zero parameters, which is the baseline-4 case; the schema is empty and fully described. The description correctly implies a parameterless call and adds no misleading parameter talk.

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 names a specific verb and resource ('Generate a 128-bit random nonce') plus the intended use ('request correlation'), which is far more than a restatement of the title 'Secure nonce'. It stops short of naming a sibling such as privi_idempotency_key or privi_pro_nonce_replay_window, so the boundary with those tools is only implied.

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?

Usage is implied by 'for request correlation', which tells the agent the context in which to reach for it. There is no explicit when-not guidance or named alternative, and the negative clause ('not an authentication credential') rules out one misuse case but does not route the agent anywhere else.

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