Update an item in an actor's inventory. system is DEEP-MERGED into the existing data: pass only the fields you change, e.g. {"quantity": 3} or {"uses": {"value": 0}}; arrays are replaced whole.
| Name | Required | Description | Default |
|---|---|---|---|
| img | No | New icon path | |
| name | No | New item name | |
| itemId | Yes | Item ID to update (from item-list) | |
| system | No | System data to deep-merge. | |
| actorId | Yes | Actor ID that owns the item |
Changes observed during successful MCP inspections.
Input schema / properties / system / descriptionPrevious value: -"Updated system data (quantity, equipped, range, damage, uses, etc.)"New value: +"System data to deep-merge."Input schema / properties / system / properties / damage / descriptionRemoved value: -"Damage"Input schema / properties / system / properties / damage / properties / base / properties / types / descriptionRemoved value: -"e.g. [\"slashing\"]"Input schema / properties / system / properties / range / descriptionRemoved value: -"Weapon/spell range"Input schema / properties / system / properties / range / properties / long / descriptionPrevious value: -"Long range (e.g. 600)"New value: +"e.g. 600"Input schema / properties / system / properties / range / properties / reach / descriptionPrevious value: -"Melee reach in ft (default 5)"New value: +"reach ft"Input schema / properties / system / properties / range / properties / units / descriptionRemoved value: -"ft or m"Input schema / properties / system / properties / range / properties / value / descriptionPrevious value: -"Normal range (e.g. 150)"New value: +"e.g. 150"Input schema / properties / system / properties / uses / additionalPropertiesPrevious value: -falseNew value: +trueInput schema / properties / system / properties / uses / properties / max / anyOfAdded value: +[
+ {
+ "type": [
+ "number",
+ "string"
+ ]
+ },
+ {
+ "type": "null"
+ }
+]Input schema / properties / system / properties / uses / properties / max / typeRemoved value: -[
- "number",
- "null"
-]Input schema / properties / system / properties / uses / properties / per / descriptionPrevious value: -"Recovery: \"sr\", \"lr\", \"day\", \"charges\""New value: +"dnd5e 3.x"Input schema / properties / system / properties / uses / properties / recoveryAdded value: +{
+ "description": "[{ period: \"lr\" }]",
+ "items": {
+ "additionalProperties": true,
+ "properties": {
+ "period": {
+ "type": "string"
+ }
+ },
+ "required": [
+ "period"
+ ],
+ "type": "object"
+ },
+ "type": "array"
+}Input schema / properties / system / properties / uses / properties / spentAdded value: +{
+ "description": "dnd5e 4+: spent",
+ "minimum": 0,
+ "type": "integer"
+}Input schema / properties / system / properties / uses / properties / value / descriptionPrevious value: -"Remaining uses"New value: +"dnd5e 3.x"Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare that this is a non-read-only, non-destructive mutation. The description adds important behavioral detail beyond the annotations: `system` is deep-merged, only changed fields should be sent, and arrays are replaced wholesale rather than merged.
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 concise sentences with the core update behavior front-loaded. The second sentence provides merge semantics and examples without unnecessary exposition.
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?
Given the nested `system` schema and the absence of an output schema, the description provides enough context to call the tool correctly, especially around merge behavior. It does not cover permissions, errors, or return behavior, but those gaps are minor relative to the schema's richness and the annotation coverage.
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 parameters. The description still adds meaningful semantics for the `system` parameter by explaining deep-merge behavior, array replacement, and giving concrete examples such as `{"quantity": 3}` and `{"uses": {"value": 0}}`.
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 states a specific verb and resource: update an item in an actor's inventory. This clearly distinguishes it from create/delete/list item operations and from world-item-update, which is not scoped to an actor's inventory.
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?
The description implies usage by saying to update an item in an actor's inventory and by explaining how to pass changed fields. However, it does not explicitly say when to use this tool versus siblings such as item-create, item-delete, or world-item-update.
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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