Add support for publishing a NeMo Agent Toolkit workflow as a MCP server via FastMCP3

docs/source/run-workflows/fastmcp-server.md

@@ -0,0 +1,183 @@
+<!--
+SPDX-FileCopyrightText: Copyright (c) 2026, NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+SPDX-License-Identifier: Apache-2.0
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+-->
+
+# NeMo Agent Toolkit as a FastMCP Server
+
+Model Context Protocol (MCP) is an open protocol developed by Anthropic that standardizes how applications provide context to [LLMs](../build-workflows/llms/index.md). This guide covers how to run NVIDIA NeMo Agent Toolkit workflows as a FastMCP server.
+
+## Decision
+
+NeMo Agent Toolkit supports two MCP server runtimes. Both publish the same workflow tools as MCP. Choose the runtime that matches your deployment stack and organization’s MCP server policy:
+
+- Use `nat mcp serve` for the [MCP SDK server runtime](https://github.com/modelcontextprotocol/python-sdk).
+- Use `nat fastmcp server run` for the [FastMCP server runtime](https://github.com/jlowin/fastmcp).
+- For the MCP SDK server guide, see [NeMo Agent Toolkit as an MCP Server](./mcp-server.md).
+- MCP client commands and configuration require the MCP SDK package (`nvidia-nat-mcp`).
+
+## Installation
+
+Install the `nvidia-nat-fastmcp` package:
+
+```bash
+uv pip install nvidia-nat-fastmcp
+```
+
+For MCP client commands and configuration, install the `nvidia-nat-mcp` package:
+
+```bash
+uv pip install nvidia-nat-mcp
+```
+
+## FastMCP Server Usage
+
+Use `nat fastmcp server run` to start a FastMCP server and publish workflow tools.
+
+```bash
+nat fastmcp server run --config_file examples/getting_started/simple_calculator/configs/config.yml
+```
+
+This starts a FastMCP server on the default host (`localhost`) and port (`9902`) and publishes all workflow tools at `http://localhost:9902/mcp` using streamable-http transport.
+
+You can also specify server settings with CLI flags:
+
+```bash
+nat fastmcp server run --config_file examples/getting_started/simple_calculator/configs/config.yml \
+  --host 0.0.0.0 \
+  --port 9902 \
+  --name "My FastMCP Server"
+```
+
+### Using Developer Mode
+
+Use `nat fastmcp server dev` to restart the server when files change. This is useful when you iterate on workflow code or configuration.
+
+```bash
+nat fastmcp server dev --config_file examples/getting_started/simple_calculator/configs/config.yml \
+  --watch-path examples/getting_started/simple_calculator/src
+```
+
+### Filtering FastMCP Tools
+
+You can publish a subset of tools using the `--tool_names` flag:
+
+```bash
+nat fastmcp server run --config_file examples/getting_started/simple_calculator/configs/config.yml \
+  --tool_names calculator
+```
+
+### Mounting at Custom Paths
+
+To mount the server at a custom base path, set `base_path` in the configuration file:
+
+```yaml
+general:
+  front_end:
+    _type: fastmcp
+    name: "my_fastmcp_server"
+    base_path: "/api/v1"
+```
+
+With this configuration, the FastMCP server is accessible at `http://localhost:9902/api/v1/mcp`.
+
+## Inspecting and Running MCP Tools Published by a FastMCP Server
+
+Use `nat mcp client` to inspect and run tools exposed by a FastMCP server.
+
+**Note:** The `nat mcp client` commands require the `nvidia-nat-mcp` package. If you encounter an error about missing MCP client functionality, install it with `uv pip install "nvidia-nat[mcp]"`.
+
+### List all tools
+
+```console
+$ nat mcp client tool list --url http://localhost:9902/mcp
+calculator__divide
+calculator__compare
+calculator__subtract
+calculator__add
+calculator__multiply
+```
+
+### List a tool with schema
+
+```console
+$ nat mcp client tool list --url http://localhost:9902/mcp --tool calculator__multiply --detail
+Tool: calculator__multiply
+Description: Multiply two or more numbers together.
+Input Schema:
+{
+  "properties": {
+    "numbers": {
+      "description": "",
+      "items": {
+        "type": "number"
+      },
+      "title": "Numbers",
+      "type": "array"
+    }
+  },
+  "required": [
+    "numbers"
+  ],
+  "title": "Calculator__MultiplyInputSchema",
+  "type": "object"
+}
+```
+
+### Call a tool with JSON arguments
+
+```console
+$ nat mcp client tool call calculator__multiply \
+  --url http://localhost:9902/mcp \
+  --json-args '{"numbers": [1, 3, 6, 10]}'
+180.0
+```
+
+### Using the `/debug/tools/list` route (no MCP client required)
+
+```console
+$ curl -s http://localhost:9902/debug/tools/list | jq
+```
+
+## Integration with MCP Clients
+
+The FastMCP server implements the Model Context Protocol specification, so it works with MCP clients. You can run a workflow that connects to the FastMCP server by pointing an MCP client function group at `http://localhost:9902/mcp`.
+
+Example:
+
+```bash
+nat run --config_file examples/MCP/simple_calculator_fastmcp/configs/config-mcp-client.yml \
+  --input "Is 2 times 2 greater than the current hour?"
+```
+
+## Authentication
+
+FastMCP servers can validate bearer tokens using OAuth2 token introspection. Configure `server_auth` in your front end config with the introspection endpoint and client credentials.
+
+See the protected example for a full setup:
+
+- `examples/MCP/simple_calculator_fastmcp_protected`
+
+## Verifying FastMCP Server Health
+
+You can verify server health using the `/health` route or `nat mcp client ping`:
+
+```console
+$ curl -s http://localhost:9902/health | jq
+```
+
+```console
+$ nat mcp client ping --url http://localhost:9902/mcp
+```

docs/source/run-workflows/mcp-server.md

@@ -21,6 +21,21 @@ Model Context Protocol (MCP) is an open protocol developed by Anthropic that sta
 
 This guide will cover how to use NeMo Agent Toolkit as an MCP Server to publish [tools](../build-workflows/functions-and-function-groups/functions.md#agents-and-tools) using MCP. For more information on how to use NeMo Agent Toolkit as an MCP Host with one or more MCP Clients, refer to [MCP Client](../build-workflows/mcp-client.md).
 
+## Decision
+
+NeMo Agent Toolkit supports two MCP server runtimes. Both publish the same workflow tools as MCP. Choose the runtime that matches your deployment stack:
+
+- Use `nat mcp serve` for the [MCP SDK server runtime](https://github.com/modelcontextprotocol/python-sdk).
+- Use `nat fastmcp server run` for the [FastMCP server runtime](https://github.com/jlowin/fastmcp). For FastMCP server support, see [NeMo Agent Toolkit as a FastMCP Server](./fastmcp-server.md).
+
+## Installation
+
+Install the `nvidia-nat-mcp` package:
+
+```bash
+uv pip install nvidia-nat-mcp
+```
+
 ## MCP Server Usage
 
 The `nat mcp serve` command can be used to start an MCP server that publishes the [functions](../build-workflows/functions-and-function-groups/functions.md) from your [workflow](../build-workflows/about-building-workflows.md) as MCP tools.

examples/MCP/simple_auth_mcp/configs/config-mcp-auth-jira-per-user.yml

@@ -27,8 +27,6 @@ authentication:
     _type: mcp_oauth2
     server_url: ${CORPORATE_MCP_JIRA_URL}
     redirect_uri: ${NAT_REDIRECT_URI:-http://localhost:8000/auth/redirect}
-    default_user_id: ${NAT_USER_ID}
-    allow_default_user_id_for_tool_calls: ${ALLOW_DEFAULT_USER_ID_FOR_TOOL_CALLS:-true}
 
 llms:
   nim_llm:

examples/MCP/simple_calculator_fastmcp/README.md

@@ -0,0 +1,75 @@
+<!--
+SPDX-FileCopyrightText: Copyright (c) 2026, NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+SPDX-License-Identifier: Apache-2.0
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+-->
+
+# Simple Calculator - FastMCP
+
+**Complexity:** 🟢 Beginner
+
+This example demonstrates how to run the NVIDIA NeMo Agent Toolkit as a FastMCP server and use those tools from a Model Context Protocol (MCP) client workflow.
+
+This example mirrors the `simple_calculator_mcp` workflow, but it uses the FastMCP server command and defaults to port `9902`. The FastMCP server integration comes from `nvidia-nat-fastmcp`, and the MCP client commands and configuration use `nvidia-nat-mcp`.
+
+## Prerequisites
+
+- **Agent toolkit**: Ensure you have the NVIDIA NeMo Agent Toolkit installed. If you have not already done so, follow the instructions in the [Install Guide](../../../docs/source/get-started/installation.md#install-from-source) to create the development environment and install the toolkit.
+- **Base workflow**: This example builds upon the Getting Started [Simple Calculator](../../getting_started/simple_calculator/) example. Make sure you are familiar with the example before proceeding.
+
+## Installation and Setup
+
+If you have not already done so, follow the instructions in the [Install Guide](../../../docs/source/get-started/installation.md#install-from-source) to create the development environment and install the toolkit.
+
+### Install this Workflow
+
+Install this example:
+
+```bash
+uv pip install -e examples/MCP/simple_calculator_fastmcp
+```
+
+## Run the Workflow
+
+1. Start the FastMCP server:
+
+```bash
+nat fastmcp server run --config_file examples/getting_started/simple_calculator/configs/config.yml
+```
+
+This starts a FastMCP server on port `9902` with endpoint `/mcp` and uses `streamable-http` transport.
+
+2. Inspect the tools available on the FastMCP server using the MCP client:
+
+```bash
+nat mcp client tool list --url http://localhost:9902/mcp
+```
+
+Sample output:
+
+```text
+calculator__add
+calculator__subtract
+calculator__multiply
+calculator__divide
+calculator__compare
+```
+
+3. Run the workflow:
+
+```bash
+nat run --config_file examples/MCP/simple_calculator_fastmcp/configs/config-mcp-client.yml --input "Is the product of 2 * 4 greater than the current hour of the day?"
+```
+
+The client configuration is in `examples/MCP/simple_calculator_fastmcp/configs/config-mcp-client.yml`.

examples/MCP/simple_calculator_fastmcp/configs/config-mcp-client.yml

@@ -0,0 +1,68 @@
+# SPDX-FileCopyrightText: Copyright (c) 2026, NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# This config file shows how to use MCP servers as NeMo Agent Toolkit tools.
+# It connects to a local MCP server with stdio transport and a FastMCP server
+# using streamable-http transport.
+
+# This config file shows -
+# 1. how to use a local MCP server to get the current date and time using stdio transport.
+# 2. how to access a FastMCP server using streamable-http transport for math operations.
+#
+# As the mcp_server_time is running locally ensure that the package "mcp_server_time" is installed
+# on your local machine. For example, if you are using pip, you can install it with:
+# uv pip install mcp-server-time
+
+function_groups:
+  mcp_time:
+    _type: mcp_client
+    server:
+      transport: stdio
+      command: "python"
+      args: ["-m", "mcp_server_time", "--local-timezone=America/Los_Angeles"]
+    tool_overrides:
+      # Optionally override the tool name and description from the MCP server
+      get_current_time:
+        alias: get_current_time_mcp_tool
+        description: "Returns the current date and time"
+
+  mcp_math:
+    _type: mcp_client
+    server:
+      transport: streamable-http
+      url: "http://localhost:9902/mcp"
+    include:
+      - calculator__add
+      - calculator__subtract
+      - calculator__multiply
+      - calculator__divide
+      - calculator__compare
+
+llms:
+  nim_llm:
+    _type: nim
+    model_name: meta/llama-3.1-70b-instruct
+    temperature: 0.0
+    max_tokens: 1024
+
+workflow:
+  _type: react_agent
+  tool_names:
+    - mcp_time
+    - mcp_math
+  llm_name: nim_llm
+  verbose: true
+  retry_parsing_errors: true
+  max_retries: 3