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

Annotations already signal a non-read-only, non-idempotent, non-destructive write, so the description doesn't need to restate that. It adds genuinely non-obvious behavior: a per-IP-per-month throttling rule and the fact that the credential is returned once and is secret, which changes how an agent must handle the response. It stops short of explaining what happens on a throttled attempt (error shape, wait guidance).

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 compact sentences with zero filler, front-loading the action and then the terms. Every clause carries decision-relevant information: limits, expiry, no card, one-time secret return.

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?

With no input parameters and no output schema, the description covers the essentials, including the critical one-time-return behavior that an output schema would otherwise have to document. It omits how the key is used afterward (header format, auth scheme), a minor gap for a zero-arg provisioning tool.

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?

There are zero parameters, so the baseline is 4; nothing in the schema needs explaining. The description correctly implies the tool takes no input, and the constraints it lists (IP, monthly window) are server-derived rather than arguments.

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 ("Create a free FluxProof API key") and immediately qualifies it with the entitlement: one page, checked daily, 30 days, no card. It is plainly the key-provisioning tool, distinct from siblings like fluxproof_create_monitor or fluxproof_offer.

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 conveys when this is relevant by describing the free-tier offering and its limits, which implies you call it before any authenticated work. However, it never explicitly says to call this first, nor does it point to the alternatives (e.g. fluxproof_preflight or fluxproof_offer) or state what to do if you already hold a key.

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