Fill a box

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

With no annotations, the description carries the full burden, and it does well: it discloses behavioral distinctions between modes, including item drops for destroy, interior untouched for outline, and automatic splitting over the 32768-block command limit. It does not explicitly state that the operation modifies the world or that snapshots are taken by default, but the schema's dry_run and snapshot parameters cover some of that.

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?

Two sentences, front-loaded with the core action, then compactly packed mode semantics and the auto-split behavior. There is no filler or redundant restatement of schema fields.

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 10-parameter tool with no output schema, the description plus the schema covers the essential behaviors: modes, replace filtering, auto-splitting, snapshot control, dry run, and world selection. The main missing piece is an explicit statement of the expected result/return value, but that is not critical for invocation.

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 70%, and the description adds real meaning to the mode enum and replace_filter by explaining what each mode does. It does not clarify the from/to coordinate interpretation, though the schema's array-of-3-integers type provides a baseline hint.

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 clearly states the tool's action: 'Fill a box with one block' and enumerates the five modes, making the resource and operation specific. It does not explicitly distinguish fill from sibling tools like build or place_shape, so it stops short of a 5.

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 mode list gives implied usage context: choose replace when you want optional filtering, keep for air-only, destroy to drop items, etc. However, there is no explicit guidance about when to use fill instead of build, place_shape, or paste_schematic, and no exclusion criteria or when-not-to-use guidance.

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