Changelog

All notable changes to MCP/U are documented in this file.

v1.2.1 - Client Runtime Version Metadata

Released: 2026-05-15

mcpu-client runtime version reporting - package 1.2.0 still advertised client/server runtime version 1.1.0; 1.2.1 reports the published npm version.

Released: 2026-05-15

McpPolling(ms) — firmware-declared auto-poll (MCP-U_Arduino)
- New McpPollConfig struct and McpPolling(interval_ms) helper
- Register a tool with mcp.add_tool("name", "desc", handler, McpPolling(2000))
- Firmware emits "polling": {"enabled": true, "interval_ms": N} in list_tools
- Client reads the interval and schedules calls automatically — no env vars needed
- Buffer results (type: "buffer") from polled tools are written to memory as observations

writeResource crash on startup (mcpu-client) — missing unit, data_type, sampling_enabled, and metadata_json fields caused "Missing named parameter unit" error
sql_readonly_query and memory_status tools not registering — previously gated on memory && readonlyAdapter; both tools now always register with null-safe handlers so the LLM can always call them (and get a descriptive error if memory is unavailable)
get_pin_summary, get_pin_buffer, get_pin_events schema — pin parameter was declared as "string" which caused MCP Inspector and clients to send "34" instead of 34, failing the _find_pin() lookup; now correctly declared as "integer"

Released: 2025-11-01

SQLite memory subsystem (mcpu-client)
- Local mcpu-memory.db stores all sensor observations, tool calls, and buffer drains
- sql_readonly_query MCP tool — LLM can query history with raw SQL (SELECT/WITH only)
- memory_status MCP tool — returns driver status, row counts, poller health
- mcu://cache/schema, mcu://cache/status, mcu://cache/examples MCP resources
Buffer Drain Poller — automatically drains pin ring buffers from ESP32 into memory based on capabilities.buffer + sampling metadata discovered via list_tools
Env-var auto-poll (MCPU_AUTO_POLL_<TOOLNAME>=<ms>) — workaround for custom tools before firmware-declared polling was available (superseded by McpPolling in v1.2.0)
Retention config — MCPU_RAW_RETENTION_HOURS, MCPU_TOOL_CALL_RETENTION_DAYS

Released: 2025-05-01

MCP-U Firmware Library (McpIot)
- JSON-RPC 2.0 protocol implementation over Arduino Stream
- Built-in tools: get_info, list_tools, gpio_write, gpio_read, pwm_write, adc_read
- Custom tool registration via McpDevice::registerTool()
- Pin registry with type support (digital_output, digital_input, pwm_output, adc_input)
- JSON Schema generation for all tools
Transport Support
- Serial (UART) — primary transport, USB-UART
- TCP (WiFi) — ESP32 WiFiClient server mode
Client (mcpu-client)
- TypeScript MCP server implementation
- Dynamic tool discovery via list_tools
- JSON Schema to Zod conversion at runtime
- Multi-device support with device ID prefixing
- Serial and TCP transport abstraction
Platform Support
- ESP32 (all variants) — full support
- ESP8266 — full support
- Arduino AVR (Uno, Mega, Nano) — limited RAM support
- RP2040 (Pico) — experimental
Documentation
- Starlight documentation site
- Architecture reference
- Protocol specification
- Client setup guides
- Firmware development guide
- Compatibility matrix