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

Annotations indicate readOnlyHint=false, destructiveHint=false, and idempotentHint=false. The description confirms it's a mutation (rolling initiative) but doesn't elaborate on side effects like overwriting existing initiative values or setting turn order. Since annotations are minimal, the description carries some burden but only partially fulfills it.

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 sentences, zero wasted words. The primary purpose is front-loaded, followed by ordering guidance and a flag hint. Every sentence 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?

The description covers the essential usage: what it does, when to call it, and the key flag. It doesn't describe the return value, but no output schema exists and the tool is simple enough that this isn't critical. The schema handles parameter details like combatId defaulting. Adequate for the tool's complexity.

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 schema already documents all three parameters. The description adds value by explaining the npcsOnly flag's rationale ('to let players roll their own'), which goes slightly beyond the schema's 'Only roll for NPCs, skip player characters'. This practical context justifies a score above baseline.

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 clearly states a specific verb and resource: 'Roll initiative for all combatants at once.' It distinguishes itself from the sibling combat-roll-initiative (singular) by emphasizing 'all at once', making the tool's purpose unambiguous.

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 provides explicit ordering context ('Call AFTER combat-add-combatant, BEFORE combat-start') and explains the npcsOnly flag's purpose. While it doesn't explicitly mention the singular combat-roll-initiative as an alternative, the 'all at once' phrasing and naming make the distinction clear. Slight deduction for not naming the alternative directly.

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