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

Annotations already declare readOnlyHint, idempotentHint, and non-destructive, so the safety profile is covered. The description adds substantial behavior beyond that: the exact categories of output (failing expectations with actual values and timing, visible changes, dispenser shots, breakage notes) and what happens when the optional test is omitted. It stops short of stating runtime limits or cost, but that is minor for a sandbox simulation.

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 the output contract, then the sibling routing rule — a sensible order. The output enumeration is dense but every clause names a distinct result category; the only mild bloat is listing example visible-change types.

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?

No output schema exists, so the description must carry the return contract, and it does in concrete terms. Combined with a deep nested input schema, an agent has everything needed to decide when to call it and how to interpret results.

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 100% and the nested 'test' object is thoroughly documented, so the schema does the heavy lifting. The description still adds value the schema does not: it frames 'test' as optional and explains that omitting it produces a plain run-and-report, which clarifies the default behavior of the only parameter.

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 specific verb and resource ('Run a redstone design with its own test') plus the exact result shape: which expectations hold, what visibly changed, dispenser shots, and breakage notes. It explicitly separates itself from the sibling 'show', so an agent can choose between them without opening schemas.

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?

Gives both a positive rule ('Use it on every candidate before showing it') and an explicit exclusion with the alternative named ('Do not use it to display a design to the user: use show'). It also covers the no-test fallback case, so no usage mode is left to inference.

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