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

Annotations already declare this is a non-read-only, non-idempotent, non-destructive mutation, and the description usefully adds that the change is written to the log, that temp HP is consumed first, and that healing is clamped at max. It does not say what happens on invalid input (e.g., healing an unconscious participant) or whether passing both damage and heal is allowed, so beyond annotations it is helpful but partial.

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?

A single dense sentence covering mechanics, logging, and authorization, followed by the return value. Nothing is padded, though the parenthetical asides are slightly compressed to the point of terseness.

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 mutation tool with full schema coverage and no output schema, the description covers mechanics, side effects (logging), authorization, and return value ("The battle"). Remaining gaps are minor: error behavior and the damage/heal mutual-exclusivity question.

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 five parameters are already documented; the description only adds semantic nuance for damage (temp HP first) and heal (capped at maximum). It does not clarify the relationship between the optional damage and heal fields, which the schema leaves ambiguous (neither is required).

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 names the concrete operation (apply damage or healing to a battle participant) and even specifies the resolution rules: temporary hit points absorb damage first and healing caps at the maximum. It is clearly distinct from siblings like update_participant or mark_character_fallen, though it never explicitly contrasts itself with them.

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?

"GM only" gives a clear permission precondition, which is real usage guidance. However, there is no statement of when to reach for this versus update_participant, mark_character_fallen, or revive_character, and no exclusion of edge cases such as out-of-combat healing.

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