serial-mcp

by davidalo

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Python

Local

read_until

Reads data from a serial port until a specified terminator string is received, enabling line-based protocol handling.

Instructions

Read from serial port until a terminator string is received.

Useful for reading line-based protocols (terminator='\n').

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "port_id": "<port_id>"
    },
    "name": "read_until"
  }
}

Input Schema

Name	Required	Description	Default
`port_id`	Yes	The port identifier
`terminator`	No	Stop reading when this string is received
`timeout`	No	Maximum time to wait in seconds
`max_bytes`	No	Maximum bytes to read
`encoding`	No	Encoding for terminator and output	utf-8

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.4.0Jun 10, 2026

TDQS

A3.6/5.0

Behavior2/5

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

No annotations are provided, so the description must disclose behavioral traits. It does not state whether the tool is blocking, what happens on timeout (returns partial data or fails), or if it is read-only. This leaves significant ambiguity for an AI agent.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is two sentences, front-loading the core logic. Every sentence is useful and there is no wasted text.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness2/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

No output schema is provided, and the description does not indicate what the tool returns (e.g., a string, bytes, or a structured result). It also lacks error handling details, timeout behavior, and preconditions like port being open.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The input schema covers all 5 parameters with descriptions, so the baseline is 3. The description adds minor usage context (e.g., terminator='\n' for lines) but no additional semantic meaning beyond what the schema provides.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the tool reads from a serial port until a terminator string is received. This distinguishes it from siblings like read_bytes (fixed count) and read_for_duration (time-based) by specifying the stopping condition.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description gives a concrete usage example (line-based protocols with terminator='\n'), helping the agent decide when to use this tool. However, it does not explicitly mention when not to use it or suggest alternatives, though sibling names provide some context.

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

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