Sends a single text or HEX message to an already connected serial port, enabling device command input or log-triggering; connect the port first with connect_serial.
Send one message to a serial port. The port must already be connected with connect_serial.
| Name | Required | Description | Default |
|---|---|---|---|
| data | Yes | Text or HEX string to send | |
| port | Yes | Target port | |
| hex_mode | No | Send as hexadecimal bytes |
Changes observed during successful MCP inspections.
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations exist, so the description carries the full burden. It discloses the connection prerequisite and the single-shot nature of the call, but says nothing about failure behavior when the port is not connected, delivery guarantees, or whether the write is buffered.
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 short sentences with zero waste, and the action statement is front-loaded ahead of the prerequisite.
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 simple three-parameter, fully documented write tool with no output schema, the essential precondition is covered. The remaining gap is error/failure semantics, which an agent would need when the port is not connected.
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 port, data, and hex_mode are already documented in structured fields. The description adds no parameter-level detail beyond those, which is the expected baseline when the schema does the work.
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 and resource ('Send one message to a serial port') with a scope word ('one message') that implicitly separates it from the batch sibling start_auto_send. It does not name that sibling, so the differentiation is left for the agent to infer.
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?
Gives an explicit precondition that names the sibling to call first ('The port must already be connected with connect_serial'). It stops short of stating when to prefer this over start_auto_send for repeated sends, so usage coverage is clear but not complete.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.