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

Annotations cover the safety profile (readOnlyHint, openWorldHint), and the description adds genuinely useful behavioral context beyond them: the drand/League of Entropy source, the beacon round enabling independent re-verification, and a concrete $0.002 USDC per-call cost via x402. Cost and verifiability are exactly the kind of traits annotations cannot express. It omits error/failure behavior, which keeps it from a 5.

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: source first, then the two modes, then verifiability and price. Each clause carries real information with no filler, though the long run-on construction slightly hurts scannability.

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 5-parameter tool with no output schema and only 20% schema coverage, the description covers purpose, cost, and verification but leaves the salt parameter, count defaults, and result shape undocumented. Adequate but with clear gaps an agent would hit when invoking it.

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 only 20% (low), so the description must compensate. It conceptually maps to min/max ("numbers in a range"), items and count ("shuffle and pick of your items"), but leaves salt completely unexplained and gives no formats, bounds, or inclusivity rules. It recovers roughly half the gap, not enough for a 4.

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+resource: verifiable random numbers from the drand beacon, with two concrete modes (range, shuffle/pick). The purpose is unmistakable, but the description never differentiates itself from any sibling (e.g. decide, calc, fun), so it stops short of a 5.

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 only implied through the enumerated capabilities (range vs. shuffle/pick of items); there is no explicit when-to-use, when-not-to-use, or named alternative. An agent can infer the two scenarios but gets no routing guidance.

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