regions

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

readOnlyHint=true already declares the safety profile, but the description adds what the listing surfaces (status values like running/done/waiting, exit status, line range, file) — useful behavioral context beyond the annotation. No pagination or ordering caveats beyond the implied 'most recent', which is minor.

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, front-loaded with the core action, followed by purpose-driven use cases. No filler; every clause conveys a distinct piece of information.

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?

An output schema exists, so return-value detail is not required, and the description still sketches the region fields well enough for selection. Combined with the safety annotation and full schema coverage, nothing an agent needs to invoke it correctly is missing.

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 both parameters (last, session) are already documented in the schema. The description implies recency and session scoping but adds no format or edge-case detail beyond that. Baseline 3 is appropriate when the schema carries the parameter burden.

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 (List) and resource (regions), then defines exactly what a region is: command/program input with status, exit status, line range, and file. This gives an agent a clear mental model distinct from the session/command siblings.

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?

Explicitly enumerates three concrete when-to-use scenarios: finding a region id for read/search, checking on a running command without waiting, and seeing what a human or another agent ran. This routes the agent to correct usage rather than leaving it to infer.

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