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

With no annotations, the description carries the full burden and does well: it discloses the RNG mechanism (platform CSPRNG with rejection sampling), guarantees fairness per face, notes the non-deterministic nature of the output, and reveals pricing ($0.005/call via x402 in USDC). It stops short of detailing error behavior or latency, but the behavioral picture is unusually complete.

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 short sentences, front-loaded with the purpose and return value, then mechanism, then cost. The rejection-sampling remark is a slight detour but is short and justifies the fairness claim, so it earns its place.

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?

A zero-required-parameter, non-deterministic tool with no output schema; the description compensates by describing the return (all rolls plus total), the fairness guarantee, and the payment cost. Little that an agent needs in order to call it correctly is missing.

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% (count 1-100 default 1; faces 2-1000000 default 6), so the schema already documents both parameters and the baseline is 3. The '3d6' notation adds only loose flavor, and it does not map cleanly onto the two separate count/faces fields.

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 ('Roll dice with any number of faces') and explicitly names what is returned ('every roll plus the total'). The dice/faces framing differentiates it in substance from random_number or random_coinflip, though it never names those siblings directly.

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?

There is no statement of when to choose this over the other random_* tools (coinflip, number, pick, shuffle). The only usage-flavored content is the notation example '3d6, 1d20', which is syntax rather than selection guidance, and there are no exclusions or prerequisites.

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