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Place a block

place_block
Destructive

Place a single voxel block at a grid cell, using the same box brush humans use. This is how you BUILD - adding blocks is the default and the action you want almost every time. Coordinates are integer grid cells. World map: wx=gx0.5, wy=2.0+gy0.5, wz=gz*0.5. gy=0 is the first solid block layer (world y=2.0). One block per cell. Player-parity: must be within ~15m of where you stand AND the cell must touch the ground or an existing solid block. op defaults to 'add'. Set op:'remove' ONLY to clear a SOLID block that already exists and is in your way - removing an empty cell is rejected as nothing-to-remove and wastes the turn, so never remove on open ground. Failure returns { ok:false, reason, suggested_stand? }. reason is one of: "not-adjacent" (the cell has no solid neighbour below or beside it - it would float; build out from existing blocks), "out-of-reach" (you are too far - move_to(suggested_stand) then retry), "out-of-claim" (outside your buildable area), "material-not-allowed", "nothing-to-remove" (op:remove on empty air), "rate-limited". Only inside your claim, allowed material, additive unless granted destructive.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
gxYes
gyYes
gzYes
opNoadd
spaceYes
materialYesA material KEY/name string (e.g. "calacatta-gold", "western-red-cedar") OR a numeric id. There are ~146 materials and the ids are SPARSE (non-contiguous, gaps throughout the 0..186 range), so do NOT guess an id - call get_material_palette and pass a returned key.

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed1 schema field changed
    • addedInput schema / additionalProperties
      Added value: +false
  2. First observed

TDQS

A4.8/5.0
Behavior5/5

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

The description thoroughly explains behavioral traits beyond annotations: coordinate mapping, adjacency/reach/claim constraints, material restrictions, and failure modes. Annotations already indicate destructive and non-readonly, and description adds context on when removal is appropriate.

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?

The description is dense and informative with no wasted sentences, but could be more structured (e.g., bullet points) for easier scanning. Still, it earns its length.

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

Completeness4/5

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

The description covers constraints, failure modes, and usage nuances. However, it omits the success response structure and does not explicitly address placing a block where one already exists (whether it fails or replaces). Given the complexity, a minor gap.

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

Parameters5/5

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

With only 17% schema coverage, the description compensates by explaining gx/gy/gz as integer grid cells with world coordinate mapping, op default and behavior, and material constraints. This adds significant meaning beyond the schema stubs.

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?

The description clearly states the tool places a single voxel block using a box brush, specifying it is the default build action. It distinguishes itself from the 'remove' operation and implies it is the granular action compared to sibling tools like 'build'.

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

Usage Guidelines5/5

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

The description provides explicit guidance: op defaults to 'add', use 'remove' only to clear existing solid blocks, avoid removing empty cells. It explains failure reasons and suggests actions like building from existing blocks or moving closer.

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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