Five tools with complete input schemas and descriptions, but significant gaps in output documentation and error guidance. Tool names follow verb_noun pattern (arduino_serial_*) which is clear. Descriptions are present (avg ~100 chars) but lack context on when to use each tool vs. alternatives, prerequisites, and what happens on failure. No output schemas documented, LLMs cannot plan downstream calls or extract structured data. Error handling is minimal: tools throw generic ToolError without recovery guidance. Parameters lack constraints (e.g., baud rate has no min/max, port has no format hint). No mention of idempotency, side effects, or retry safety. Composition is reasonable (each tool does one thing), but missing chaining IDs in responses and no pagination for potential multi-port scenarios.

• Document output schemas for all tools. E.g., arduino_serial_open should return {port: string, baudRate: int, status: 'open'}. arduino_serial_read should return {lines: string[], count: int, timestamp: ISO8601}.
• Add parameter constraints: baud as enum [300, 600, 1200, 2400, 4800, 9600, 19200, 38400, 57600, 115200] or min/max; lines as integer min=1 max=1000; port as string pattern matching /^/dev\/.*/ or similar.
• Enhance error messages with recovery guidance. E.g., 'No serial ports open. Call arduino_serial_open(port="/dev/cu.usbmodem14101", baud=115200) first.' instead of generic ToolError.
• Add context to descriptions: 'Use arduino_serial_read to fetch buffered output after sending commands. Call arduino_serial_status to check connection state without consuming buffer.' Clarify when each tool is appropriate.
• Document idempotency and side effects. E.g., 'arduino_serial_write appends newline and sends immediately, retrying with same text sends duplicate command. Use arduino_serial_read(clear=false) to inspect buffer before sending.' Mark as destructive/non-idempotent.