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

Beyond the annotations (readOnlyHint=false, destructiveHint=false, openWorldHint=true), the description discloses a rich behavioral trait: the idle watchdog that auto-stops the stream and disconnects the device after idle_timeout_sec of no polling, that any poll resets the timer, and that 0 disables it. It also explains the safety rationale (a live stream on the user's head) and the confirm gate, which the annotations alone do not convey.

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?

The action and confirm gate are front-loaded in the first two sentences, and the watchdog explanation follows logically. It is somewhat longer than strictly necessary given the schema already documents idle_timeout_sec, but every sentence carries usable 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 values need not be explained, and the annotations cover the safety profile. Combined with prerequisites, the tracking workflow, and the watchdog behavior, an agent has everything needed to invoke this 14-parameter tool correctly.

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 all 14 parameters, including confirm and idle_timeout_sec. The description reinforces those two with rationale but adds no new syntax or format information, so the baseline 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?

The description states a specific verb and resource ('Connect an EEG device and START a live streaming session') and is clearly distinguishable from stream.stop and stream.status by name. An agent knows exactly what this tool initiates without reading the schema.

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?

It gives explicit prerequisites ('Requires confirm=True; call device.test first') and names the tracking alternative ('Track with stream.status()'), which is strong routing guidance. It stops short of an explicit when-not (e.g. what to do if a session is already running, or when to prefer stream.stop), so it is not a full 5.

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