Android SMS MCP Server – MCP Protocol Communication

The Android SMS MCP Server exposes SMS functionality over the Model Context Protocol (MCP), allowing any MCP-compatible AI agent to send SMS messages and query SIM card information directly through a mobile device. Communication uses Streamable HTTP transport: every request is a plain POST /mcp call and every response is a synchronous JSON reply.

System architecture

The diagram below shows the three actors involved in every MCP interaction. The AI Agent drives the conversation; the SMS MCP Server — which runs as a foreground service on the Android device — translates MCP tool calls into SMS operations; the Mobile Phone dispatches the messages over the GSM/4G/5G mobile network via its SIM card(s).

graph LR subgraph "AI Client Environment" A["AI Agent
(LLM + MCP Client)"] end subgraph "Local Network 192.168.0.11:9531" S["Android SMS
MCP Server"] end subgraph "Mobile Device" P["Mobile Phone
(Android)"] SIM1["SIM Slot 0
Vodafone UK"] SIM2["SIM Slot 1
Yettel HU"] P --> SIM1 P --> SIM2 end A -- "POST /mcp JSON-RPC 2.0" --> S S -- "JSON response" --> A S -- "SMS via mobile network" --> P

Protocol transaction pages

The MCP session follows a fixed lifecycle. Click each step below to see the full HTTP request/response pair, a field-level explanation, and a sequence diagram.

# Transaction JSON-RPC method Description
1 Initialize the MCP session initialize Negotiate protocol version and exchange capability declarations between client and server.
2 List available tools tools/list Retrieve the full catalogue of tools the server exposes, including their input schemas.
3 Get SMS subscriptions tools/call -> get_sms_subscriptions Query the active SIM cards (subscriptions) installed in the Android device.
4 Send an SMS message tools/call -> send_sms Instruct the device to send an SMS to a given phone number via a selected SIM.

To sum it up

The Android SMS MCP Server turns a mobile phone into a network-accessible SMS gateway without any custom integration work on the AI agent side. Any agent that speaks MCP can discover the available tools automatically via tools/list, choose the right SIM via get_sms_subscriptions, and dispatch messages via send_sms — all over a simple HTTP connection on your local network.

More information