serial_open

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

With no annotations, the description carries the full burden. It discloses exclusive access and the default baud rate, and hints that a previous session must be closed before calling. However, it omits important behaviors such as what happens if the port is already open or unavailable, whether the call blocks, and what it returns on success or failure.

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 concise sentences with no filler. The core purpose is front-loaded, and the additional instruction about closing previous sessions is brief and critical. The mention of 'Ratchet UART' provides small but useful context without bloating the description.

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 tool with no output schema and no annotations, the description should explain the outcome and possible failure modes. It tells the agent what the tool does and a prerequisite, but not what it returns, how errors are signaled, or how the opened port is referenced by subsequent sibling calls. This leaves gaps for an agent that needs to chain actions.

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?

The schema covers 100% of the parameters with meaningful descriptions ('Serial port path, e.g. COM3' and 'Baud rate (default 115200)'). The description adds no new parameter information beyond repeating the default baud, so it neither enhances nor detracts from the schema.

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?

Clearly states the operation: 'Open a serial port exclusively for read/write.' This is a specific verb and resource, and it distinguishes itself from siblings like serial_read, serial_write, and serial_close by being the opening operation. The mention of exclusive access adds precision.

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?

Provides a key prerequisite: 'Close any previous session first,' which tells the agent to use serial_close before opening if needed. It implies that only one session can be active at a time, but it does not explicitly contrast with alternatives or state when not to use this tool (e.g., if already open).

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