fill

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

With no annotations, the description carries the full load. It does disclose important behavior: the mutation semantics of each mode and that state 'void' clears positions (a destructive effect). It omits which structure is targeted (the 'name' parameter is unexplained), whether this requires an opened structure, and whether the change is undoable despite an 'undo' sibling existing.

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?

Front-loaded with the core action, then a compact mode table in one sentence, then the void-clearing note. Dense and waste-free; slightly terse given how much parameter surface is undocumented.

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?

The output schema covers return values, so no credit is needed there. But for a 9-parameter mutating tool with 0% schema coverage, missing target-structure semantics and coordinate/name documentation leave real gaps before an agent can call it confidently.

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 0%, so the description must compensate, and it does document all five mode enum values plus the 'void' clearing behavior for state, which is genuinely beyond the schema. But it says nothing about the 'name' parameter, the x1/y1/z1 vs x2/y2/z2 pairing, or coordinate conventions, leaving the majority of 9 parameters undocumented anywhere.

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?

States a concrete verb and resource ('Fill a box') with a scope qualifier ('inclusive corners'), which tells an agent exactly what the operation affects. It does not distinguish itself from siblings like set_blocks or replace_blocks, which also write blocks, so the agent must infer the boundary.

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 enumeration gives implicit guidance: an agent can pick 'replace' vs 'hollow' vs 'walls' from the described semantics. However, there is no statement of when to prefer fill over set_blocks/replace_blocks/copy_region, no mention that a structure must already be open, and no exclusions or prerequisites.

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