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

Annotations declare non-readonly, non-idempotent, non-destructive, so the mutation profile is known; the description adds valuable facts beyond that: the exact state transition (round 1, turn 0), the return of combat state, and what includeContext appends (a combat-next-turn block). It does not address what happens if called on an already-started combat (reset vs. error), a meaningful gap for a non-idempotent op.

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 core action and state, followed by timing and return behavior. No filler.

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 compensates by stating that combat state is returned and what includeContext adds. Remaining ambiguity is about error/re-entry behavior on an already-running combat, which an agent would need for a non-idempotent 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 description coverage is 100%, so both parameters are already documented in the schema; the description's only added semantic is naming the appended payload 'as combat-next-turn,' which is a small but real elaboration over 'Append tactical context (default true).' Baseline 3 for fully covered params is appropriate.

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 ('Begin combat') plus exact resulting state (round 1, turn 0), which immediately separates it from combat-create, combat-next-turn, and combat-set-turn in the sibling list.

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?

Explicit sequencing guidance: 'Call AFTER adding combatants and rolling initiative,' which tells the agent the prerequisite steps. It does not name the sibling tools that satisfy those prerequisites (combat-add-combatant, combat-roll-all-initiative) or say what to do if no combat exists yet, so it falls short of full alternative routing.

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