Tavern

Edit a custom item

update_custom_item

DestructiveIdempotent

Replace a custom item's details. Returns: The item.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "campaign": "<campaign>",
      "character": "<character>",
      "item": "<item>"
    },
    "name": "update_custom_item"
  }
}

Input Schema

Name	Required	Description
`cost`	No	Value.
`icon`	No	A glyph key from the app's icon set.
`item`	Yes	The item's id.
`name`	No	What it is called.
`slot`	No	Where it is worn, for equipment.
`armor`	No	Armor numbers.
`magic`	No	Whether it is magical.
`detail`	No	The whole text.
`rarity`	No	How rare it is.
`weight`	No	Weight.
`acBonus`	No	Armor class it adds while worn.
`effects`	No	Up to eight effect lines.
`summary`	No	One line for the card.
`campaign`	Yes	The campaign, by its slug (what its link says) or its id.
`itemType`	No	A short type line, in your own words.
`quantity`	No	How many.
`statLine`	No	A stat line for the card.
`character`	Yes	The character, by its slug.
`equipment`	No	True for something worn or wielded, false for counted gear.
`requiresAttunement`	No	Whether it needs attuning.

Schema Changelog

Changes observed during successful MCP inspections.

First observedNov 3, 2026

TDQS

C2.6/5.0

Behavior2/5

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

The annotations already declare destructiveHint=true and idempotentHint=true, so the safety profile is known. The description adds only 'Returns: The item.' and does not explain the behavior that matters for a destructive replace: whether omitted fields are wiped, whether required identifiers must match an existing item, or what happens on a non-existent id.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Two short sentences with the action front-loaded and the return value stated compactly; nothing is padded. It is efficient, though the brevity crosses into under-specification rather than crispness.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness2/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a 20-parameter, nested-object, destructive mutation with no output schema and slug-based identifiers, the description is far too thin. It should state replacement semantics and identifier resolution, which are the main sources of incorrect invocation here.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100% across 20 parameters, including enums and nested armor fields, so the schema carries the load and the baseline of 3 applies. The description adds no parameter-level meaning beyond the word 'Replace', which leaves the partial-vs-full-update question around the 17 optional parameters unresolved.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose3/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description names a verb ('Replace') and resource ('custom item's details'), which is enough to distinguish it from read-only siblings like get_character. However, 'Replace' is ambiguous: it does not say whether the whole item is overwritten or only supplied fields are merged, which is the single most important thing an agent needs to know about this tool.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines2/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

There is no when-to-use guidance at all. The sibling list contains add_custom_item and update_homebrew_box, and the description gives no cue about choosing between creating, editing, or homebrewing an item, nor any precondition such as the item already existing.

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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