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remove_mass_trait_from_entity

Destructive

Remove an FMassTag from a Mass entity in the editor world via archetype migration; all entities sharing that archetype also lose the tag.

Instructions

Remove an FMassTag from a Mass entity of the editor world (not PIE) by archetype migration; inverse of add_mass_trait_to_entity. Caveat: the tag is removed from EVERY entity sharing that archetype, not only this one. Returns old_archetype_id, new_archetype_id and changed (false when nothing moved).

Returns: { entity_handle, old_archetype_id, new_archetype_id, tag, changed }

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
tagYesReflected name of the FMassTag struct to remove, without the F prefix, as list_mass_trait_types returns it (e.g. "MassOffLODTag"); /Script paths do not resolve
entity_handleYesEntity handle as "Index:SerialNumber", two integers such as "12:3" (no braces); a no-longer-valid entity is an error

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed2 schema fields changedv1.2.0
    • changedInput schema / properties / entity_handle / description
      Previous value: -"\"{Index}:{SerialNumber}\""New value: +"Entity handle as \"Index:SerialNumber\", two integers such as \"12:3\" (no braces); a no-longer-valid entity is an error"
    • changedInput schema / properties / tag / description
      Previous value: -"UScriptStruct name/path (the tag to remove)."New value: +"Reflected name of the FMassTag struct to remove, without the F prefix, as list_mass_trait_types returns it (e.g. \"MassOffLODTag\"); /Script paths do not resolve"
  2. First observedv1.1.0

TDQS

A4.5/5.0
Behavior5/5

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

Annotations already flag destructiveHint=true and idempotentHint=false, but the description adds the crucial blast-radius caveat: the tag is removed from EVERY entity sharing the archetype, not only the named one. That is exactly the kind of non-obvious side effect annotations cannot express, plus the changed flag indicates no-op behavior.

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

Conciseness5/5

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

Front-loads the action, then the caveat, then the return shape in two tight sentences. Every clause carries information: scope, inverse reference, blast radius, and return fields.

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

Completeness5/5

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

No output schema exists, so naming the returned fields (old_archetype_id, new_archetype_id, changed and the false-when-nothing-moved semantics) is genuinely necessary and supplied. Combined with the scope limit and archetype-wide caveat, an agent has everything needed to invoke this correctly.

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%, so both parameters are already fully documented in the schema (tag naming convention, entity_handle 'Index:SerialNumber' format). The description only reinforces 'FMassTag', adding little beyond the structured data; baseline 3 applies.

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

Purpose5/5

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

States a specific verb+resource+scope: removing an FMassTag from a Mass entity by archetype migration, restricted to the editor world (not PIE). It also names the inverse operation (add_mass_trait_to_entity), so an agent can distinguish direction of travel immediately.

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

Usage Guidelines4/5

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

Explicitly bounds the usage context with 'editor world (not PIE)' and points at the inverse tool, which tells the agent when this direction is appropriate. It does not, however, disambiguate against the nearby sibling remove_mass_trait, which an agent could reasonably confuse with this one.

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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