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

Goes well beyond the annotations: it names the random source (cryptographic), states the return payload (every roll, the modifier, the total), documents the input bounds, discloses cost and the first-25-free / failed-calls-free policy, and explicitly reconciles the readOnlyHint=false annotation by explaining that charging makes each call non-read-only.

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?

Front-loads the core behavior and bounds before secondary details, and every sentence carries information. It is dense — the pricing and read-only-justification clause is a lot for one paragraph — but nothing is redundant.

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 single-parameter tool with no output schema, the description covers input syntax, bounds, randomness guarantees, return contents, and cost. An agent has everything needed to invoke it and set expectations for the response.

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%, so the baseline is 3, but the description adds real constraints the schema lacks: notation format, the 100-dice/1000-sides caps, and the 1d6 default. That meaningfully extends the field description rather than restating it.

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 such as 2d6+3 or 1d20') with hard bounds (up to 100 dice of up to 1000 sides). This clearly separates it from siblings like random_number, coin, and magic_8_ball without needing to open any schema.

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?

Gives an explicit usage domain ('Use for tabletop games and simulations') and shows a concrete example call. It stops short of naming when NOT to use it or pointing to a sibling alternative, but the intended context is unambiguous.

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