Find the supply

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

readOnlyHint=true already tells the agent this is safe, so the description's real contribution is the Bluetooth exclusion and the hidden stateful effect: the answering port is cached for later calls. That caching behavior is the kind of side effect an agent needs and cannot get from the annotations, though nothing is said about latency per port or failure when no device responds.

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 compact sentences with no filler; the core action comes first and the caching consequence follows. Every clause carries information: what is listed, what is probed, what is skipped, and what persists.

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?

For a single-optional-parameter discovery tool with no output schema, this covers the action, the probe target, the exclusion, and the stateful side effect. It falls short only on edge behavior such as returning an empty list or timing out when no PP300S answers.

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 max_wall is already documented with bounds and a default in the schema. The description adds no extra meaning about the timeout, so the baseline of 3 applies.

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+resource: lists serial ports and probes each USB one for a PP300S status, with Bluetooth ports excluded. An agent can tell this is a discovery/probe tool rather than a control tool like 'set' or 'output', though no sibling is named to sharpen the boundary.

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 sentence 'The port that answers is remembered for later calls' implies this is the first step before using set/output/status, but the guidance is indirect. There is no explicit when-to-use statement and no when-not or alternative mentioned, such as what to do if you already know the port.

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