Roll dice in standard notation such as 3d6+2 and return the individual rolls and total. Pure CPU, instant.
Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.
{
"id": 1,
"jsonrpc": "2.0",
"method": "tools/call",
"params": {
"arguments": {
"dice": "<dice>"
},
"name": "dice"
}
}| Name | Required | Description | Default |
|---|---|---|---|
| dice | Yes | Notation such as 3d6+2 |
Changes observed during successful MCP inspections.
Input schema / properties / diceAdded value: +{
+ "description": "Notation such as 3d6+2",
+ "type": "string"
+}Input schema / requiredAdded value: +[
+ "dice"
+]Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full burden, but it does add real value: it discloses the return contents ('individual rolls and total') and the performance profile ('pure CPU, instant'). It omits error behavior for malformed notation (e.g., '3x6') and any determinism/seeding notes, which are the remaining behavioral questions an agent would have.
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?
Two short sentences with zero filler; the core action and notation example come first, and the performance note is a useful trailing detail rather than padding.
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 one-parameter deterministic tool with no output schema, disclosing the return shape (individual rolls + total) is exactly the right level of detail. Only the handling of invalid notation is left unaddressed.
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 the single parameter is already documented as a string with notation format, and the description merely restates the same '3d6+2' example. Baseline 3 applies since the schema does the semantic work.
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 (roll) and resource (dice) plus a concrete notation example, 'such as 3d6+2', which makes it distinguishable from generic RNG siblings like random_number or coinflip. It does not explicitly name those siblings as alternatives, so it stops short of full differentiation.
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 when-to-use or when-not-to-use guidance, and no mention of why an agent would pick this over random_number or another randomness sibling. Usage is only implied by the word 'Roll'.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
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