fill_terrain

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

With no annotations, the description carries the full burden of behavioral disclosure. It describes the operation but does not reveal whether the fill is destructive, replaces existing terrain, is reversible (e.g., via undo), or requires any permissions. For a mutation tool, this lack of transparency is a significant gap.

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?

The description is a single concise sentence that names the action, resource, material, and shape options. Every element contributes to understanding the tool's core function without unnecessary words.

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?

While the description covers the central operation, it is thin for a mutation tool with no annotations or output schema. It omits behavioral context (e.g., whether it overwrites existing terrain, if it returns a success indicator, any side effects) that would help the agent plan its use. The rich schema mitigates some gaps but cannot fully compensate.

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?

The schema provides complete descriptions for all four parameters, including nested X/Y/Z fields and the shape enum. The description adds no additional parameter semantics beyond what the schema already offers, so a baseline score of 3 is appropriate.

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 action ('fill'), the target ('region of terrain'), the material, and the shape options, distinguishing it from siblings like clear_terrain (which removes terrain) and object creation tools. It also mentions the available shapes, matching the enum in the schema.

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 description implies the use case of filling a terrain region but provides no explicit guidance on when to choose this tool over alternatives like clear_terrain or create_object. There are no exclusions or alternative references, leaving the agent to infer usage from the tool name and operation.

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