Adding MCP call (via HTTP)

dsl-reference.md

@@ -15,6 +15,7 @@
         + [HTTP](#http-call)
         + [OpenAPI](#openapi-call)
         + [A2A](#a2a-call)
+        + [MCP](#mcp-call)
     - [Do](#do)
     - [Emit](#emit)
     - [For](#for)
@@ -322,6 +323,7 @@ Serverless Workflow defines several default functions that **MUST** be supported
 - [HTTP](#http-call)
 - [OpenAPI](#openapi-call)
 - [A2A](#a2a-call)
+- [MCP](#mcp-call)
 
 ##### AsyncAPI Call
 
@@ -527,6 +529,71 @@ do:
                 text: Generate the Q1 sales report.
 ```
 
+##### MCP Call
+
+The [MCP Call](#mcp-call) enables workflows to interact with MCP servers that are used by AI agents (https://modelcontextprotocol.io/).
+
+###### Properties
+
+| Name | Type | Required | Description|
+|:--|:---:|:---:|:---|
+| method | `string` | `yes` | The MCP JSON-RPC method to send.<br>*Supported values are: `initialize`, `notifications/initialized`, `prompts/list`, `prompts/get`, `notifications/prompts/list_changed`, `resources/list`, `resources/read`, `resources/templates/list`, `notifications/resources/list_changed`, `tools/list`, `tools/call`, `notifications/tools/list_changed`, `logging/setLevel`, and `notifications/message`* |
+| server | `string`\|[`endpoint`](#endpoint) | `yes` | An URI or an object that describes the MCP server to call.<br>|
+| parameters | `map` <br> `string` | `no` | The parameters for the MCP RPC method. For the `initialize` method, runtimes must default `protocolVersion` to the used version.<br>*Can be an object or a direct runtime expression.* |
+
+> [!NOTE]
+> On success the output is the JSON-RPC result. On failure runtimes must raise an error with type [https://serverlessworkflow.io/spec/1.0.0/errors/runtime](https://github.com/serverlessworkflow/specification/blob/main/dsl-reference.md#standard-error-types).
+>
+> This call only supports MCP over HTTP transport mechanism and not STDIO (communication over standard in and standard out).
+
+###### Examples
+
+This example shows an initialization phase as the first interaction between MCP client and server. The client sends its supported version, capabilities, and implementation informationin the initialize request. The server MUST respond with its own capabilities and information including the supported version.
+
+```yaml
+document:
+  dsl: '1.0.1'
+  namespace: test
+  name: mcp-example
+  version: '0.1.0'
+do:
+  - GenerateReport:
+      call: mcp
+      with:
+        method: initialize
+        server:
+          endpoint: https://example.com/mcp
+        parameters:
+          protocolVersion: '2025-03-26'
+          capabilities:
+            roots:
+              listChanged: true 
+          clientInfo:
+            name: 'ExampleClient'
+            version: '1.0.0'
+```
+
+The following example showcases a prompts/list request by the client to retrieve available prompts from the MCP server.
+
+```yaml
+document:
+  dsl: '1.0.1'
+  namespace: test
+  name: mcp-example
+  version: '0.1.0'
+do:
+  - GenerateReport:
+      call: mcp
+      with:
+        method: prompts/get
+        server:
+          endpoint: https://example.com/mcp
+        parameters:
+          name: "code_review"
+          arguments:
+            code: "def hello():\n    print('world')"
+```
+
 #### Do
 
 Serves as a fundamental building block within workflows, enabling the sequential execution of multiple subtasks. By defining a series of subtasks to perform in sequence, the Do task facilitates the efficient execution of complex operations, ensuring that each subtask is completed before the next one begins.
@@ -2706,4 +2773,4 @@ References a workflow definition.
 name: greet
 namespace: samples
 version: '0.1.0-rc2'
-```
+```

dsl.md

@@ -597,6 +597,7 @@ Serverless Workflow DSL is designed to seamlessly interact with a variety of ser
 - [**AsyncAPI**](dsl-reference.md#asyncapi-call): Facilitates interaction with asynchronous messaging protocols. AsyncAPI is designed for event-driven architectures, allowing workflows to publish and subscribe to events.
 - [**OpenAPI**](dsl-reference.md#openapi-call): Enables communication with services that provide OpenAPI specifications, which is useful for defining and consuming RESTful APIs.
 - [**A2A**](dsl-reference.md#a2a-call): Enables interaction with A2A servers (agents described by A2A).
+- [**MCP**](dsl-reference.md#mcp-call): Enables interaction with MCP servers.
 
 Runtimes **must** raise an error with type `https://serverlessworkflow.io/spec/1.0.0/errors/communication` if and when a problem occurs during a call.
 
@@ -815,4 +816,4 @@ sampleOAuth2:
 
 These authentication schemes can be defined globally in the authentication section or associated with specific endpoints. They provide secure access to resources while ensuring proper authorization and identity verification.
 
-See the [DSL reference](dsl-reference.md#authentication) for more details about authentication.
+See the [DSL reference](dsl-reference.md#authentication) for more details about authentication.

schema/workflow.yaml

@@ -473,6 +473,41 @@ $defs:
                   description: The parameters object to send with the A2A method.
               required: [ method ]
               unevaluatedProperties: false
+      - title: CallMCP
+        description: Defines the MCP call to perform.
+        type: object
+        unevaluatedProperties: false
+        required: [ call, with ]
+        allOf:
+        - $ref: '#/$defs/taskBase'
+        - properties:
+            call:
+              type: string
+              const: mcp
+            with:
+              type: object
+              title: MCPArguments
+              description: The MCP call arguments.
+              properties:
+                server:
+                  title: MCPServer
+                  description: The MCP server endpoint to send the request to.
+                  $ref: '#/$defs/endpoint'
+                method:
+                  type: string
+                  title: WithMCPMethod
+                  description: The MCP method to send.
+                  enum: [ 'initialize', 'notifications/initialized', 'prompts/list', 'prompts/get', 'notifications/prompts/list_changed', 'resources/list', 'resources/read', 'resources/templates/list', 'notifications/resources/list_changed', 'tools/list', 'tools/call', 'notifications/tools/list_changed', 'logging/setLevel', 'notifications/message' ]
+                parameters:
+                  oneOf:
+                    - type: object
+                      minProperties: 1
+                      additionalProperties: true
+                    - type: string
+                  title: WithMCPParameters
+                  description: The parameters object to send with the MCP method.
+              required: [ method, server ]
+              unevaluatedProperties: false              
       - title: CallFunction
         description: Defines the function call to perform.
         type: object
@@ -1823,4 +1858,4 @@ $defs:
       export:
         $ref: '#/$defs/export'
         title: SubscriptionIteratorExport
-        description: An object, if any, used to customize the content of the workflow context.
+        description: An object, if any, used to customize the content of the workflow context.