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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false, so the agent knows this is a safe read. The description adds the local/runtime-backed scoping and the hint that it lists 'executable' libraries, which is useful. However, it doesn't describe pagination or ordering behavior. With annotations covering safety, a 3 is appropriate – it adds some context but not deep behavioral detail.

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 with no redundancy. The core action and scope are front-loaded, and the differentiation is stated concisely. Every word earns its place.

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?

Given the tool's simplicity (2 optional params, no output schema, no nested objects) and the annotations covering safety, the description is sufficient for correct invocation. It could be slightly stronger by mentioning that the list might be large or the result is ordered, but for a list tool with full schema coverage, it is complete enough.

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%, so the schema already documents both parameters (limit and search) with their meanings. The description does not add extra parameter details, which is acceptable given full schema coverage. The baseline of 3 applies here.

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 states a specific verb ('List') and resource ('executable local-runtime Mojo libraries'), and explicitly distinguishes itself from governed data/query tools. This clearly differentiates it from sibling tools like list_datasets or list_sources.

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 clearly tells the agent when to use this tool ('when you need the runtime-backed compute catalog') and what it is NOT ('rather than the governed data/query tools'). However, it does not explicitly name alternative tools like list_runtime_modules or execute_runtime_library as alternatives, which would strengthen the guidance.

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