http1c — MCP Server Framework for 1C:Enterprise

http1c is a framework for building Model Context Protocol (MCP) servers from 1C:Enterprise. It provides a native component (DLL) that handles the MCP transport layer and a reference 1C data processor that demonstrates how to implement tools, resources, and prompts.

Use it as a template to expose any 1C business logic — catalogs, documents, reports, calculations — to AI applications like VS Code Copilot, Claude Desktop, and other MCP-compatible clients.

Core Concept

The project is intentionally split into two layers with different responsibilities.

Native component responsibilities

The DLL is the MCP engine. It handles protocol and transport details that should not be reimplemented in 1C business code:

• HTTP/SSE transport
• JSON-RPC request/response lifecycle
• MCP session management
• authentication, origin validation, and rate limiting
• pagination, notifications, and progress streaming
• converting 1C responses into valid MCP replies

1C responsibilities

The 1C side owns business logic. A 1C developer should work at the level of tools, resources, and prompts, not at the level of MCP internals:

• describe a tool/resource/prompt in BSL
• register it in the component
• handle the incoming call in 1C
• run any required client-side or server-side 1C logic
• return the result or send progress updates

Why the project is designed this way

The goal is to let a 1C developer publish almost any 1C functionality through MCP without having to understand HTTP, JSON-RPC, SSE, session handling, or MCP message formatting.

In other words:

• the component knows how to be an MCP server
• 1C knows what the tool actually does

This keeps the integration point simple. To add new functionality, a 1C developer does not need to change the native transport layer. They only add or update 1C definitions and handlers.

Mental model for a 1C developer

From the 1C side, the workflow is intentionally simple:

1. Define the MCP object in BSL.
2. Register it in the component.
3. Receive the request through ExternalEvent.
4. Execute arbitrary 1C logic.
5. Return the final result, and optionally send progress while the operation is running.

This means the project is not a fixed set of built-in utilities. It is an MCP transport and protocol layer for 1C, with the actual application behavior defined in 1C code.

Key Features

• Full MCP protocol support — tools, resources, prompts with listChanged notifications
• Streamable HTTP transport — POST /mcp for requests, GET /mcp for SSE notification stream
• Session management — Mcp-Session-Id header, UUID v4 sessions per spec
• Security — Origin validation (DNS rebinding protection), Bearer token auth, rate limiting
• Progress streaming — SSE-based progress notifications for long-running operations
• Pagination — cursor-based pagination for tools/list, resources/list, prompts/list
• Tool annotations — readOnlyHint, destructiveHint, idempotentHint, openWorldHint
• Output schemas — typed response contracts for tool results
• Dynamic registration — register/update tools, resources, prompts at runtime from 1C
• Built-in semantic search (RAG) — optional search / grep / get_segment / list_collections tools backed by a Rust search core (rcore) with dense/keyword/hybrid retrieval (see Search Subsystem)

Architecture

┌─────────────────┐     HTTP/SSE      ┌──────────────────┐    ExternalEvent   ┌──────────────────┐
│   MCP Client    │◄─────────────────►│   Native DLL     │◄──────────────────►│  1C:Enterprise   │
│  (VS Code, etc) │   POST/GET /mcp   │  (HttpServer)    │   ToolCall, etc.   │  (BSL Module)    │
└─────────────────┘                   └──────────────────┘                    └──────────────────┘

1. A 1C form loads the native add-in and starts the HTTP server.
2. An MCP client connects to http://localhost:PORT/mcp.
3. The native component handles protocol-level messages (initialize, tools/list, etc.).
4. Business logic requests (tools/call, resources/read, prompts/get) are forwarded to 1C via ExternalEvent.
5. The 1C module processes the request and sends results back through SendResponse.
6. The DLL wraps the result in a JSON-RPC response and returns it to the client.

Quick Start

1. Build the DLL

build/build-http1c-dll-release.sh

Requires Visual Studio Build Tools 2019+ with C++ support.

2. Package the add-in

Packaging is done automatically at the end of the build script. To run it standalone:

build/package-http1c-addin.sh

3. Compile the EPF (requires OneScript)

build/compile-http1c-epf.sh

4. Open in 1C

1. Open the http1c.epf data processor in your 1C infobase. The MCP server starts automatically on open (attaches the component, registers the tool / resource / prompt catalogs, and begins listening on port 8888 by default).
2. To restart it on a different port, set the port field and click Connect. (The Connect button remains available for manual control.)
3. Configure your MCP client to connect to http://localhost:PORT/mcp.

5. VS Code configuration

Add to your .vscode/mcp.json:

Without authentication:

{
  "servers": {
    "1c-mcp-server": {
      "type": "sse",
      "url": "http://localhost:8888/mcp"
    }
  }
}

With Bearer token authentication:

{
  "servers": {
    "1c-mcp-server": {
      "type": "sse",
      "url": "http://localhost:8888/mcp",
      "headers": {
        "Authorization": "Bearer ${input:mcpToken}"
      }
    }
  },
  "inputs": [
    {
      "id": "mcpToken",
      "type": "promptString",
      "description": "Bearer token for the 1C MCP server",
      "password": true
    }
  ]
}

When using the ${input:...} syntax, VS Code will prompt for the token each time the MCP server connection starts. The entered value is masked as a password.

Important: The token in VS Code must match the value set on the 1C side. If the server has no token configured (empty string), authentication is disabled and no headers are needed. If a token is set on the server but VS Code sends no Authorization header, the server responds with HTTP 401 and VS Code may try to start an OAuth flow — this is not supported; use the headers approach above instead.

How to Build Your Own MCP Server from 1C

The reference data processor (http-1c-dp) is a working example. Use it as a starting point:

Registering Tools

Tools are executable functions that AI clients can invoke. Define them as JSON structures and register with the component:

// Create a tool definition
Tool = NewTool("myTool", "Description of what this tool does");
AddToolParam(Tool, "paramName", "string", "Parameter description");
AddToolAnnotations(Tool, True);  // readOnly, safe

// Define output schema (optional, helps clients validate responses)
Schema = NewOutputSchema();
AddOutputProperty(Schema, "result", "string", "Result description");
SetToolOutputSchema(Tool, Schema);

// Register all tools
Tools = New Array;
Tools.Add(Tool);
Await Component.RegisterToolsAsync(SerializeToJson(Tools));

Handle the tool call in the ExternalEvent handler:

&AtClient
Async Procedure ExternalEvent(Source, Event, Data)
    If Source <> "HttpServer" Then Return; EndIf;
    If Event = "ToolCall" Then ProcessToolCall(Data); EndIf;
EndProcedure

Registering Resources

Resources provide contextual data to AI clients (metadata, file contents, etc.):

Resource = New Structure;
Resource.Insert("uri", "1c://metadata/catalogs");
Resource.Insert("name", "1C Catalogs");
Resource.Insert("description", "List of all catalog metadata objects");
Resource.Insert("mimeType", "application/json");

Resources = New Array;
Resources.Add(Resource);
Await Component.RegisterResourcesAsync(SerializeToJson(Resources));

Handle resource reads via "ResourceRead" events.

Registering Prompts

Prompts are reusable interaction templates:

Prompt = New Structure;
Prompt.Insert("name", "analyzeData");
Prompt.Insert("description", "Prompt for analyzing 1C data");

PromptArgs = New Array;
Arg = New Structure("name,description,required", "topic", "Analysis topic", False);
PromptArgs.Add(Arg);
Prompt.Insert("arguments", PromptArgs);

Prompts = New Array;
Prompts.Add(Prompt);
Await Component.RegisterPromptsAsync(SerializeToJson(Prompts));

Handle prompt gets via "PromptGet" events.

Dynamic Updates

Call RegisterToolsAsync() / RegisterResourcesAsync() / RegisterPromptsAsync() again at any time with an updated list. The component will automatically send notifications/tools/list_changed (or equivalent) to all connected MCP clients.

Security Configuration

The component supports optional Bearer token authentication. When a token is set, every HTTP request must include the Authorization: Bearer <token> header or it will be rejected with HTTP 401.

// Enable authentication — all requests must include Authorization: Bearer my-secret-token
Component.AuthToken = "my-secret-token";

// Disable authentication — any request is accepted
Component.AuthToken = "";

How it works:

| Server token | Client header | Result | |---|---|---| | Empty (default) | None needed | All requests accepted | | "my-secret" | Authorization: Bearer my-secret | Request accepted | | "my-secret" | Missing or wrong token | HTTP 401 Unauthorized |

Changing the token at runtime: You can set or clear AuthToken while the server is running. The change takes effect immediately for all new requests — no restart needed.

VS Code note: If the server returns 401, VS Code may attempt an OAuth 2.0 PKCE authorization flow (redirecting to /authorize). This is not supported by the component. Always configure the token in .vscode/mcp.json via the headers field (see VS Code configuration above).

The component also enforces:

• Origin validation — only requests from localhost / 127.0.0.1 / VS Code origins are accepted
• Rate limiting — token-bucket algorithm (60 burst, 20/sec)
• Session management — Mcp-Session-Id assigned on initialize, validated on subsequent requests. A request presenting an unknown session id is not rejected with 404 — the session is transparently resurrected under the presented id, so a server restart does not strand connected MCP clients that never re-initialize (logged as MCP: unknown session ... resurrected (server restart?))

Native Component API

Methods exposed to 1C (English / Russian names). All of these are callable asynchronously from BSL via the platform-generated BeginCalling<Name> wrappers (BeginCallingStartListen, …):

| Method | Description | |--------|-------------| | StartListen(port) / НачатьПрослушивание | Start the HTTP server on the given port | | StopListen() / ОстановитьПрослушивание | Stop the server and unblock all pending requests | | SendResponse(json) / ОтправитьОтвет | Send the final response for a pending request | | SendProgress(id, progress, total, message) / ОтправитьПрогресс | Send a progress notification for a pending request | | ApplyConfig(json) / ПрименитьНастройки | Async-safe config sink (see below). Applies any subset of logging_enabled, log_path, timeout, tools_json, resources_json, prompts_json, auth_token in one call | | GetStatus() / ПолучитьСтатус | Async-safe read of the status JSON (same payload as the Status property) | | RagDispatch(method, payload) / RagВыполнить | Drive the Rust search core (rcore) — see Search Subsystem | | TakeScreenshot(pid, format, quality, grayscale) / СделатьСкриншот | Capture windows of a process as base64 images | | GetProcessId() / ПолучитьИдентификаторПроцесса |