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

Annotations only declare the read/write/idempotency profile; the description goes well beyond them by disclosing the cryptographic random source, capacity limits (100 dice of up to 1000 sides), the exact shape of the response, and — critically — that each successful call costs $0.001 USDC on Base via x402, which an agent must know before invoking.

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?

Four dense sentences, each carrying distinct load: notation and limits, output shape, use case, and price. The action is front-loaded and nothing is repeated from the schema or annotations.

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 output schema, the description correctly compensates by describing the return payload (every roll, modifier, total), and it covers cost and limits. It omits edge behavior such as what happens with malformed notation, which is the only meaningful gap for this simple 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?

Schema coverage is 100% and the single optional parameter is already documented with a default, so baseline is 3. The description adds genuine meaning by bracketing valid inputs (up to 100 dice of up to 1000 sides) and reinforcing the notation format with examples.

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 in standard notation') with concrete examples (2d6+3, 1d20) and hard limits, so the agent knows exactly what the tool produces. It does not differentiate itself from adjacent randomness siblings such as random_number or random_pick, which is the only thing keeping it from 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?

'Use for tabletop games and simulations' gives explicit use-case context rather than leaving usage implied. It stops short of naming when NOT to use it or pointing to an alternative generator for non-dice randomness, so it lacks the exclusions a 5 would require.

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