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

Annotations already declare readOnly, idempotent, non-destructive, and closed-world, so the safety profile needs no restating. The description adds useful content-level context (the catalogue is small and fixed, with concrete examples) and routes block retrieval elsewhere. It does not say whether results are names, ids, or objects, which is the one behavioral 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?

Three short sentences with zero waste: purpose, then the concrete contents, then usage and the redirect. The most decision-relevant information is front-loaded.

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?

With no output schema, the description should hint at what comes back; naming the example designs partially does that, and the get_example redirect is the critical missing piece an agent would otherwise get wrong. Minor gap: unclear whether the list returns names, ids, or descriptions to feed into get_example.

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?

Zero parameters, so the baseline is 4; there is nothing for the description to disambiguate. It correctly says nothing about parameters rather than padding.

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 ("List the built-in example designs") and immediately enumerates the actual contents (clocks, counters, piston door, lock, flying machine), so the agent knows exactly what domain objects come back. It explicitly distinguishes itself from the sibling get_example.

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 the positive case ("Use it to find a known-good starting point") and an explicit exclusion with the alternative named ("Do not use it to fetch a design's blocks: use get_example"). The when/when-not/alternative triad is fully present.

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