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

With no annotations, the description carries the full burden and does substantial work: it discloses determinism (same seed always yields the same output), the verifiability property of the proof, the per-call price, and a free-call allowance. It stops short of describing auth/payment flow mechanics or failure behavior, but the core behavioral profile an agent needs is present.

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?

Three sentences, front-loaded with purpose, then determinism, then cost. Every sentence carries distinct information and nothing is restated.

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?

There is no output schema, so the description must imply the return value; it does so ('an ECVRF output ... plus a proof'), and it covers cost and the free tier. It could say slightly more about the proof's format or how to verify it offline, but for a two-parameter tool it is close to complete.

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 both parameters (seed, num_bytes) are already documented in the schema, and the description adds only the framing that the draw is 'bound to' the seed. No syntax, format, or constraint detail beyond the schema is supplied, matching the baseline for fully-covered schemas.

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 ('verifiable random bytes') and pins down the mechanism (ECVRF output over your seed plus an offline-checkable proof) as well as the intended use cases (draw, raffle, tie-break). No sibling tool in the list does anything comparable, so an agent can select it unambiguously.

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?

It states the scenario that calls for this tool (draws, raffles, tie-breaks) and adds a procedural hint: publish the seed first so the result can be shown as not picked. It gives no explicit when-not-to-use guidance, but the sibling set contains no competing randomness or invocation tool, so there is little to exclude.

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