Apply damage or healing to a combatant's hit points, accounting for temporary HP and maximum, and mark them down at zero. Returns new HP and status.
改某 combatant 的 HP（delta<0 伤害：临时HP先抵、夹到0；delta>0 治疗：不超 max）。 到 0 标 status=down。返回新 hp + status。
| Name | Required | Description | Default |
|---|---|---|---|
| delta | Yes | ||
| variant | No | main | |
| campaign | Yes | ||
| encounter | Yes | ||
| combatant_id | Yes |
Changes observed during successful MCP inspections.
v0.1.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are provided, so the description carries the full burden. It explicitly explains damage mechanics (temp HP absorbs first, clamps to 0), healing cap (max), side effect (status=down when HP reaches 0), and return value (new hp + status). This is thorough and transparent about the tool's behavior.
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?
The description is two sentences with no fluff. It front-loads the purpose, then explains the delta rules and side effects, then states the return value. Every sentence earns its place, and it is concise without being under-specified.
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 simple mutation tool with no annotations and no output schema, the description covers the essential information: what it does, the mechanics of delta, the side effect of reaching zero, and the return value. It does not mention error handling or prerequisites (e.g., combatant must exist in encounter), but these are not critical for calling the tool correctly. It is complete enough for an agent to use it without further information.
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 0%, so the description must compensate. It explains the delta parameter well (negative for damage, positive for healing, temp HP logic, max cap). Campaign, encounter, and combatant_id are self-evident from their names and context, but the variant parameter (with default 'main') is not explained at all. The description adds value for delta but leaves variant unexplained.
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?
Description clearly states the tool modifies a combatant's HP with a delta, specifying damage vs healing behavior. It is specific about the resource (HP) and the action (apply change), but does not explicitly differentiate from siblings like resolve_attack or roll_damage, which also affect HP indirectly. Purpose is clear and 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?
No guidance on when to use this tool versus alternatives. It does not mention that this is a direct HP modification tool as opposed to attack resolution or damage rolling. The only implied usage is from the description's mechanics, but there is no explicit when-to-use or when-not-to-use guidance.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.