Build an MCP

Build, test, and publish a Cendriix MCP (Modular Capability Provider) — the plugin system that gives agents access to external services.

What is an MCP?

An MCP is a containerised plugin exposing a typed toolset. Each tool has a name, input/output schema, and handler. Agents can only invoke tools in their permitted list.

File layout


my-mcp/
├── manifest.yaml
├── src/
│   ├── index.ts
│   ├── tools/
│   │   ├── listItems.ts
│   │   └── createItem.ts
│   └── auth.ts
├── Dockerfile
└── package.json

Manifest schema


name: my-mcp
version: 1.0.0
description: Short description
 
tools:
  - name: listItems
    description: List all items
    input:
      type: object
      properties:
        filter: { type: string }
    output:
      type: array
 
  - name: createItem
    description: Create an item
    input:
      type: object
      required: [title]
      properties:
        title: { type: string }
        body: { type: string }

Tool handler interface


interface ToolContext {
  input: Record<string, unknown>;
  secrets: Record<string, string>;
  logger: Logger;
  runId: string;
  workspaceId: string;
}
type ToolHandler = (ctx: ToolContext) => Promise<ToolResult>;

Authentication

Credentials are injected via environment variables at container start:

API key — MCP_SECRET_API_KEY
OAuth — MCP_SECRET_OAUTH_TOKEN (refresh handled by runtime)
AWS IAM — assume-role credentials via STS

Packaging and publishing


docker build -t my-mcp:1.0.0 .
docker push registry.cendriix.ai/mcps/my-mcp:1.0.0
cendriix mcp publish --manifest manifest.yaml --image registry.cendriix.ai/mcps/my-mcp:1.0.0