feat(http): add OpenAPI 3.1.0 specification and REST tool execution endpoint

README.md

@@ -274,17 +274,45 @@ In `claude_desktop_config.json` or clients connecting directly via SSE URL:
 }
 ```
 
-#### Open WebUI (Streamable HTTP)
-In Open WebUI (**Admin Panel > Settings > External Tools** or **User Settings > Tools**):
-1. Click **+** (Add Connection).
-2. Select **Type**: `MCP (Streamable HTTP)`.
-3. Set **URL**:
-   - In Docker Compose on the same network: `http://openproject-mcp:3000/mcp` (or `http://openproject-mcp:3000/sse`)
+### Open WebUI
+
+Open WebUI supports two connection modes for `openproject-mcp`:
+
+#### Option 1: MCP (Streamable HTTP) — Recommended
+1. Navigate to **Admin Panel > Settings > External Tools** (or **User Settings > Tools**).
+2. Click **+** (Add Connection).
+3. Select **Type**: `MCP (Streamable HTTP)`.
+4. Set **URL**:
+   - In Docker Compose on shared network: `http://openproject-mcp:3000/mcp` (or `http://openproject-mcp:3000/sse`)
    - From host machine: `http://localhost:3000/mcp`
-4. Set **API Key / Auth Header** (optional):
-   - If `OPENPROJECT_API_KEY` is configured in the server container environment, no key is needed in the client.
-   - For multi-user environments, pass `Bearer <your-openproject-api-key>` or append `?apiKey=<your-key>`.
-5. Click **Verify** to test connectivity and discover tools.
+5. Set **Auth** (optional): `Bearer <your-openproject-api-key>` if multi-user, or leave blank if `OPENPROJECT_API_KEY` is configured in the container.
+6. Click **Verify Connection**.
+
+#### Option 2: OpenAPI Mode
+If your Open WebUI installation connects to tool servers using OpenAPI:
+1. Click **+** (Add Connection).
+2. Select **Type**: `OpenAPI`.
+3. Set **URL**:
+   - In Docker Compose on shared network: `http://openproject-mcp:3000/openapi.json`
+   - From host machine: `http://localhost:3000/openapi.json`
+4. Set **Auth Header** (optional): `Bearer <your-openproject-api-key>`.
+5. Click **Verify Connection**.
+
+---
+
+### Hosted Server Endpoints Reference
+
+When running `openproject-mcp` as an HTTP server (`PORT=3000`), the following endpoints are exposed:
+
+| Endpoint | Method | Protocol / Client | Description |
+| :--- | :--- | :--- | :--- |
+| `/mcp` | POST, GET, DELETE | MCP Streamable HTTP | Primary endpoint for Open WebUI, Python MCP SDK, and modern Streamable HTTP clients |
+| `/sse` | GET, POST, DELETE | MCP SSE & Streamable HTTP | Dual-purpose: `GET` establishes classic SSE stream (Cursor, Claude Desktop); `POST` handles Streamable HTTP |
+| `/messages` | POST | Classic MCP SSE | Message posting endpoint for established SSE sessions (`?sessionId=...`) |
+| `/openapi.json` | GET | OpenAPI 3.1.0 | OpenAPI specification for Open WebUI (OpenAPI mode), Swagger UI, and REST integrations |
+| `/swagger.json` | GET | OpenAPI 3.1.0 | Alias for `/openapi.json` |
+| `/api/tools/{name}` | POST | REST Tool Execution | Executes an individual tool with JSON arguments and returns structured JSON output |
+| `/health` | GET | Health Check | Service health check returning `{ status: "ok", mode: "remote-mcp" }` |
 
 ---
 

docs/ARCHITECTURE.md

@@ -207,7 +207,8 @@ openproject-mcp/
 ├── src/
 │   ├── index.ts                 # Dual-transport CLI entry point (stdio & HTTP)
 │   ├── server.ts                # Stdio MCP server factory & tool registration
-│   ├── http-server.ts           # Hosted HTTP/SSE multi-tenant server (Bun.serve)
+│   ├── http-server.ts           # Hosted HTTP/SSE/OpenAPI multi-tenant server (Bun.serve)
+│   ├── openapi-spec.ts          # OpenAPI 3.1.0 specification generator for MCP tools
 │   ├── context.ts               # RequestContext & AsyncLocalStorage
 │   ├── client/
 │   │   ├── api-client.ts        # OpenProject REST API v3 HTTP client

docs/DECISIONS.md

@@ -400,3 +400,34 @@ Key requirements for hosted operation:
 - **Negative**:
   - Requires network infrastructure (e.g. reverse proxy with TLS termination) in production to protect credentials in transit.
 
+---
+
+## ADR-017: OpenAPI 3.1.0 Specification & REST Tool Execution Bridge for OpenAPI Clients
+
+### Status
+Accepted
+
+### Context
+While modern AI platforms (such as Open WebUI v0.6.31+) natively support MCP Streamable HTTP, many external tool orchestration platforms, custom user agents, and enterprise portals only integrate with external tools via standard OpenAPI 3.0 / 3.1 REST specifications (`openapi.json` / `swagger.json`). Furthermore, users of Open WebUI who configure connections using the "OpenAPI" tool server type expect a compliant OpenAPI specification endpoint that describes available tools and routes invocations over standard HTTP POST endpoints.
+
+### Decision
+1. **Dynamic OpenAPI Specification Generator (`src/openapi-spec.ts`)**:
+   - Inspect all registered MCP tools in `allTools`.
+   - Filter out mutating tools when `config.readOnly` is true.
+   - Convert tool parameter definitions (Zod schemas) into valid OpenAPI 3.1.0 JSON schemas via `zod-to-json-schema`.
+   - Expose the specification at `GET /openapi.json` and `GET /swagger.json`.
+2. **REST Tool Execution Endpoint (`POST /api/tools/{toolName}`)**:
+   - Parse and validate tool arguments from the JSON request body against the tool's Zod schema.
+   - Extract the user's OpenProject API key using standard precedence (`Authorization: Bearer`, `X-OpenProject-Api-Key`, or server default).
+   - Execute the tool within `runWithContext` using an isolated `OpenProjectClient`.
+   - Return HTTP 200 containing both formatted MCP text content and structured parsed JSON `data`.
+
+### Consequences
+- **Positive**:
+  - Open WebUI users can seamlessly connect using either connection type: "MCP (Streamable HTTP)" at `/mcp` or "OpenAPI" at `/openapi.json`.
+  - Tools are defined once in TypeScript / Zod and automatically exposed across both MCP and OpenAPI protocols with zero duplication.
+  - Full read-only guard enforcement across both transports.
+- **Negative**:
+  - Introduces `src/openapi-spec.ts` dependency on `zod-to-json-schema`.
+
+

docs/TODO.md

@@ -106,6 +106,14 @@
   - [x] Record [ADR-016](DECISIONS.md#adr-016-hosted-remote-mcp-server-architecture-httpsse-transport--multi-tenant-credential-scoping).
   - [x] Update documentation with hosted deployment guide and remote client setups for Cursor and Claude Desktop in [README.md](../README.md).
 
+- [x] **Task 8: OpenAPI 3.1.0 Specification & REST Tool Execution Bridge**
+  - [x] Implement dynamic OpenAPI specification generator `src/openapi-spec.ts`.
+  - [x] Expose `GET /openapi.json` and `GET /swagger.json` in `src/http-server.ts`.
+  - [x] Expose REST tool execution endpoint `POST /api/tools/:toolName` with Zod parameter validation and `RequestContext` execution.
+  - [x] Add automated test coverage in `tests/http-server.test.ts`.
+  - [x] Record [ADR-017](DECISIONS.md#adr-017-openapi-310-specification--rest-tool-execution-bridge-for-openapi-clients) in `docs/DECISIONS.md`.
+  - [x] Document OpenAPI connection mode and server endpoints reference table in [README.md](../README.md).
+
 ---
 
 ## 3. Backlog & Future Phases

src/http-server.ts

@@ -17,13 +17,15 @@ import {
   type JSONRPCMessage,
   type MessageExtraInfo,
 } from "@modelcontextprotocol/sdk/types.js";
+import { z } from "zod";
 import type { AppConfig } from "./config/index.ts";
 import { OpenProjectClient } from "./client/api-client.ts";
 import { runWithContext } from "./context.ts";
-import { registerAllTools } from "./tools/index.ts";
+import { registerAllTools, allTools } from "./tools/index.ts";
 import { formatToolError } from "./tools/common.ts";
 import { OpenProjectError } from "./client/errors.ts";
 import { SERVER_NAME, SERVER_VERSION } from "./server.ts";
+import { generateOpenApiSpec } from "./openapi-spec.ts";
 
 export interface HttpServerInstance {
   server: Server<unknown>;
@@ -494,7 +496,148 @@ export async function startHttpServer(config: AppConfig): Promise<HttpServerInst
         );
       }
 
-      // 2. Classic MCP SSE endpoint: GET /sse without Mcp-Session-Id header
+      // 2. OpenAPI specification endpoint
+      if (url.pathname === "/openapi.json" || url.pathname === "/swagger.json") {
+        if (req.method !== "GET") {
+          return withCors(
+            new Response(JSON.stringify({ error: "Method not allowed" }), {
+              status: 405,
+              headers: { "Content-Type": "application/json" },
+            })
+          );
+        }
+        const spec = generateOpenApiSpec(config);
+        return withCors(
+          new Response(JSON.stringify(spec, null, 2), {
+            status: 200,
+            headers: { "Content-Type": "application/json" },
+          })
+        );
+      }
+
+      // 3. REST tool execution endpoint (OpenAPI callers)
+      if (
+        url.pathname.startsWith("/api/tools/") ||
+        url.pathname.startsWith("/tools/")
+      ) {
+        if (req.method !== "POST") {
+          return withCors(
+            new Response(JSON.stringify({ error: "Method not allowed" }), {
+              status: 405,
+              headers: { "Content-Type": "application/json" },
+            })
+          );
+        }
+
+        const toolName = url.pathname.replace(/^\/(api\/)?tools\//, "");
+        const tool = allTools.find((t) => t.name === toolName);
+        if (!tool) {
+          return withCors(
+            new Response(JSON.stringify({ error: `Tool '${toolName}' not found` }), {
+              status: 404,
+              headers: { "Content-Type": "application/json" },
+            })
+          );
+        }
+
+        if (config.readOnly && !tool.readOnly) {
+          return withCors(
+            new Response(
+              JSON.stringify({
+                error:
+                  "Operation rejected. OpenProject MCP server is running in read-only mode.",
+                code: "SERVER_READ_ONLY",
+              }),
+              {
+                status: 403,
+                headers: { "Content-Type": "application/json" },
+              }
+            )
+          );
+        }
+
+        const apiKey = extractApiKey(req, url, config.apiKey);
+        if (!apiKey) {
+          return withCors(
+            new Response(
+              JSON.stringify({
+                error:
+                  "Missing OpenProject API key. Provide via Authorization header, X-OpenProject-Api-Key header, or ?apiKey= query parameter.",
+              }),
+              {
+                status: 401,
+                headers: { "Content-Type": "application/json" },
+              }
+            )
+          );
+        }
+
+        let body: unknown = {};
+        const text = await req.text();
+        if (text.trim().length > 0) {
+          try {
+            body = JSON.parse(text);
+          } catch {
+            return withCors(
+              new Response(JSON.stringify({ error: "Invalid JSON" }), {
+                status: 400,
+                headers: { "Content-Type": "application/json" },
+              })
+            );
+          }
+        }
+
+        let args: Record<string, unknown> = {};
+        if (tool.parameters) {
+          const parseResult = z.object(tool.parameters).safeParse(body);
+          if (!parseResult.success) {
+            return withCors(
+              new Response(
+                JSON.stringify({
+                  error: "Validation error",
+                  details: parseResult.error.format(),
+                }),
+                {
+                  status: 400,
+                  headers: { "Content-Type": "application/json" },
+                }
+              )
+            );
+          }
+          args = parseResult.data as Record<string, unknown>;
+        } else if (typeof body === "object" && body !== null) {
+          args = body as Record<string, unknown>;
+        }
+
+        const client = new OpenProjectClient({ baseUrl: config.baseUrl, apiKey });
+        const toolResponse = await runWithContext(
+          { client, isReadOnly: config.readOnly },
+          () => tool.execute(args as any)
+        );
+
+        let parsedData: unknown;
+        try {
+          if (toolResponse.content?.[0]?.text) {
+            parsedData = JSON.parse(toolResponse.content[0].text);
+          }
+        } catch {}
+
+        return withCors(
+          new Response(
+            JSON.stringify({
+              content: toolResponse.content,
+              isError: toolResponse.isError ?? false,
+              ...(parsedData !== undefined ? { data: parsedData } : {}),
+            }),
+            {
+              status: 200,
+              headers: { "Content-Type": "application/json" },
+            }
+          )
+        );
+      }
+
+      // 4. Classic MCP SSE endpoint: GET /sse without Mcp-Session-Id header
       if (
         url.pathname === "/sse" &&
         req.method === "GET" &&

src/openapi-spec.ts

@@ -0,0 +1,163 @@
+/**
+ * Dynamic OpenAPI 3.1.0 Specification Generator for OpenProject MCP Tools.
+ *
+ * Exposes all registered MCP tools as standard REST operations under /api/tools/{toolName},
+ * allowing Open WebUI and OpenAPI clients to discover and invoke tools via standard HTTP.
+ */
+
+import { z } from "zod";
+import { zodToJsonSchema } from "zod-to-json-schema";
+import { allTools } from "./tools/index.ts";
+import type { AppConfig } from "./config/index.ts";
+import { SERVER_VERSION } from "./server.ts";
+
+export interface OpenApiSpec {
+  openapi: string;
+  info: {
+    title: string;
+    version: string;
+    description: string;
+  };
+  servers: Array<{ url: string; description?: string }>;
+  paths: Record<string, Record<string, unknown>>;
+  components?: {
+    securitySchemes?: Record<string, unknown>;
+  };
+  security?: Array<Record<string, unknown[]>>;
+}
+
+function determineToolTag(name: string): string {
+  if (name.includes("project")) return "Projects";
+  if (name.includes("work_package")) return "Work Packages";
+  if (name.includes("query")) return "Queries";
+  if (
+    name.includes("type") ||
+    name.includes("status") ||
+    name.includes("priority") ||
+    name.includes("user")
+  ) {
+    return "Metadata";
+  }
+  if (name.includes("openapi")) return "OpenAPI";
+  return "Tools";
+}
+
+/**
+ * Generates an OpenAPI 3.1.0 document from registered MCP tools.
+ * In read-only mode, mutating tools are excluded from the specification.
+ */
+export function generateOpenApiSpec(config: AppConfig): OpenApiSpec {
+  const isReadOnly = config.readOnly ?? false;
+  const tools = allTools.filter((tool) => !isReadOnly || tool.readOnly);
+
+  const paths: Record<string, Record<string, unknown>> = {};
+
+  for (const tool of tools) {
+    const rawShape = tool.parameters ?? {};
+    const hasParams = Object.keys(rawShape).length > 0;
+    const schema = z.object(rawShape);
+    const jsonSchema = zodToJsonSchema(schema, {
+      target: "openApi3",
+      $refStrategy: "none",
+    });
+
+    const { $schema: _discard, ...cleanSchema } = jsonSchema as Record<string, unknown>;
+
+    const path = `/api/tools/${tool.name}`;
+    paths[path] = {
+      post: {
+        operationId: tool.name,
+        summary: tool.name.replace(/_/g, " "),
+        description: tool.description,
+        tags: [determineToolTag(tool.name)],
+        requestBody: hasParams
+          ? {
+              description: `Parameters for ${tool.name}`,
+              required: true,
+              content: {
+                "application/json": {
+                  schema: cleanSchema,
+                },
+              },
+            }
+          : undefined,
+        responses: {
+          "200": {
+            description: "Successful tool execution",
+            content: {
+              "application/json": {
+                schema: {
+                  type: "object",
+                  properties: {
+                    content: {
+                      type: "array",
+                      items: {
+                        type: "object",
+                        properties: {
+                          type: { type: "string" },
+                          text: { type: "string" },
+                        },
+                      },
+                    },
+                    data: {
+                      description: "Parsed JSON response payload if applicable",
+                    },
+                    isError: { type: "boolean" },
+                  },
+                },
+              },
+            },
+          },
+          "400": {
+            description: "Invalid tool parameters or schema validation error",
+          },
+          "401": {
+            description: "Missing or invalid OpenProject API key",
+          },
+          "403": {
+            description: "Operation rejected (e.g. read-only mode guard)",
+          },
+          "404": {
+            description: "Tool or requested entity not found",
+          },
+          "500": {
+            description: "Internal server or API error",
+          },
+        },
+      },
+    };
+  }
+
+  return {
+    openapi: "3.1.0",
+    info: {
+      title: "OpenProject MCP Tools API",
+      version: SERVER_VERSION,
+      description:
+        "OpenAPI REST interface for OpenProject MCP tools. Exposes curated OpenProject tools for projects, work packages, queries, metadata, and OpenAPI introspection.",
+    },
+    servers: [
+      {
+        url: "/",
+        description: "OpenProject MCP Server",
+      },
+    ],
+    components: {
+      securitySchemes: {
+        BearerAuth: {
+          type: "http",
+          scheme: "bearer",
+          description: "OpenProject API Key provided as Bearer token",
+        },
+        ApiKeyAuth: {
+          type: "apiKey",
+          in: "header",
+          name: "X-OpenProject-Api-Key",
+          description: "OpenProject API Key provided in header",
+        },
+      },
+    },
+    security: [{ BearerAuth: [] }, { ApiKeyAuth: [] }],
+    paths,
+  };
+}

tests/http-server.test.ts

@@ -511,6 +511,128 @@ describe("Hosted Remote MCP Server (HTTP/SSE)", () => {
     expect(res.status).toBe(404);
   });
 
+  test("GET /openapi.json and GET /swagger.json return valid OpenAPI 3.1.0 specification", async () => {
+    // 1. GET /openapi.json
+    const res = await fetch(`${serverUrl}/openapi.json`);
+    expect(res.status).toBe(200);
+    expect(res.headers.get("content-type")).toContain("application/json");
+    expect(res.headers.get("access-control-allow-origin")).toBe("*");
+
+    const spec = (await res.json()) as {
+      openapi: string;
+      info: { title: string; version: string };
+      paths: Record<string, { post: { operationId: string; description: string } }>;
+    };
+    expect(spec.openapi).toBe("3.1.0");
+    expect(spec.info.title).toContain("OpenProject");
+    expect(spec.paths["/api/tools/openproject_list_projects"]).toBeDefined();
+    expect(spec.paths["/api/tools/openproject_list_projects"]?.post.operationId).toBe(
+      "openproject_list_projects"
+    );
+    expect(spec.paths["/api/tools/openproject_get_work_package"]).toBeDefined();
+
+    // 2. GET /swagger.json returns identical spec
+    const swaggerRes = await fetch(`${serverUrl}/swagger.json`);
+    expect(swaggerRes.status).toBe(200);
+    const swaggerSpec = (await swaggerRes.json()) as { openapi: string };
+    expect(swaggerSpec.openapi).toBe("3.1.0");
+  });
+
+  test("POST /api/tools/:toolName executes tool and returns JSON result", async () => {
+    // 1. Missing API key returns 401
+    const noAuthRes = await fetch(`${serverUrl}/api/tools/openproject_list_projects`, {
+      method: "POST",
+      headers: { "Content-Type": "application/json" },
+      body: JSON.stringify({ pageSize: 10 }),
+    });
+    expect(noAuthRes.status).toBe(401);
+
+    // 2. Non-existent tool returns 404
+    const notFoundRes = await fetch(`${serverUrl}/api/tools/non_existent_tool`, {
+      method: "POST",
+      headers: {
+        Authorization: "Bearer test-key",
+        "Content-Type": "application/json",
+      },
+      body: JSON.stringify({}),
+    });
+    expect(notFoundRes.status).toBe(404);
+
+    // 3. Invalid tool arguments return 400
+    const invalidArgRes = await fetch(`${serverUrl}/api/tools/openproject_get_project`, {
+      method: "POST",
+      headers: {
+        Authorization: "Bearer test-key",
+        "Content-Type": "application/json",
+      },
+      body: JSON.stringify({}), // Missing required projectId
+    });
+    expect(invalidArgRes.status).toBe(400);
+
+    // 4. Valid invocation executes tool and returns result
+    const validRes = await fetch(`${serverUrl}/api/tools/openproject_list_projects`, {
+      method: "POST",
+      headers: {
+        Authorization: "Bearer test-key",
+        "Content-Type": "application/json",
+      },
+      body: JSON.stringify({ pageSize: 5 }),
+    });
+    expect(validRes.status).toBe(200);
+    const result = (await validRes.json()) as {
+      content: Array<{ type: string; text: string }>;
+      data?: unknown;
+    };
+    expect(result.content).toBeDefined();
+    expect(result.content.length).toBeGreaterThan(0);
+    expect(result.content[0]?.type).toBe("text");
+
+    // 5. Successful data execution with mocked fetch
+    const originalFetch = globalThis.fetch;
+    try {
+      globalThis.fetch = (async (url: string | URL | Request, init?: RequestInit) => {
+        if (String(url).includes("/api/v3/projects")) {
+          return new Response(
+            JSON.stringify({
+              _embedded: {
+                elements: [
+                  { id: 1, name: "Test Project", identifier: "test-proj" },
+                ],
+              },
+              total: 1,
+              count: 1,
+              pageSize: 20,
+              offset: 1,
+            }),
+            {
+              status: 200,
+              headers: { "Content-Type": "application/hal+json" },
+            }
+          );
+        }
+        return originalFetch(url, init);
+      }) as unknown as typeof fetch;
+
+      const mockRes = await fetch(`${serverUrl}/api/tools/openproject_list_projects`, {
+        method: "POST",
+        headers: {
+          Authorization: "Bearer test-key",
+          "Content-Type": "application/json",
+        },
+        body: JSON.stringify({ pageSize: 5 }),
+      });
+      expect(mockRes.status).toBe(200);
+      const mockResult = (await mockRes.json()) as {
+        isError: boolean;
+        data?: { projects: Array<{ id: number; identifier: string }> };
+      };
+      expect(mockResult.isError).toBe(false);
+      expect(mockResult.data?.projects[0]?.identifier).toBe("test-proj");
+    } finally {
+      globalThis.fetch = originalFetch;
+    }
+  });
+
   test("CLI entrypoint (src/index.ts) boots HTTP server when --port is provided", async () => {
     const proc = Bun.spawn(
       [