Tools and Sources#

Data Source Registry#

The data_source_registry function is the single source of truth for which tools exist and which data source they belong to. It controls the UI toggles, per-message filtering, and – by default – which tools each agent receives.

functions:
  data_sources:
    _type: data_source_registry
    sources:
      - id: web_search
        name: "Web Search"
        description: "Search the web for real-time information."
        tools:
          - web_search_tool
          - advanced_web_search_tool
      - id: knowledge_layer
        name: "Knowledge Base"
        description: "Search uploaded documents and files."
        tools:
          - knowledge_search
      - id: enterprise_search
        name: "Enterprise Search"
        description: "Search Confluence, Google Drive, and more."
        requires_auth: true
        tools:
          - eci

The GET /v1/data_sources API endpoint returns these entries, which the UI renders as toggles. Clients can scope a request to a subset by passing data_sources: ["web_search"] in the WebSocket chat payload or in the body of POST /v1/jobs/async/submit; only tools belonging to selected sources are active for that request.

Tools not listed in any data source entry (e.g., utility tools like “think”) are always included regardless of filtering. Passing an explicit empty list (data_sources: []) – in the WebSocket chat payload or in a POST /v1/jobs/async/submit body – disables data-source tools while leaving those unmapped utility tools available.

Source Entry Fields#

Field	Type	Default	Description
`id`	string	required	Unique key used in API payloads and filtering (e.g., `web_search`)
`name`	string	required	Display name shown in the UI
`description`	string	`""`	Human-readable description shown in the UI
`tools`	list[string]	`[]`	NAT function names or function group names belonging to this source
`requires_auth`	bool	`false`	If `true`, the UI greys out this source until the user signs in. Use for sources that need user-level OAuth tokens (e.g., enterprise SSO). Sources that use backend API keys (Tavily, Serper) should leave this `false`.
`default_enabled`	bool	`true`	Whether the source is enabled by default when a user first loads the UI

Auto-Inherit: Agents Get All Registry Tools by Default#

When an agent’s tools list is empty (the default), it automatically inherits every tool registered in data_source_registry. This means adding a new tool or data source requires only one config change – adding it to the registry.

functions:
  # Add a tool to the registry -- all agents get it automatically
  data_sources:
    _type: data_source_registry
    sources:
      - id: web_search
        name: "Web Search"
        tools:
          - web_search_tool
          - advanced_web_search_tool
      - id: knowledge_layer
        name: "Knowledge Base"
        tools:
          - knowledge_search

  # Agents with no tools list inherit all registry tools
  intent_classifier:
    _type: intent_classifier
    llm: nemotron_llm_intent

  clarifier_agent:
    _type: clarifier_agent
    llm: nemotron_llm

  # Use exclude_tools for per-agent specialization
  shallow_research_agent:
    _type: shallow_research_agent
    llm: nemotron_llm
    exclude_tools:
      - advanced_web_search_tool    # shallow uses regular web search

  deep_research_agent:
    _type: deep_research_agent
    orchestrator_llm: nemotron_llm_deep
    exclude_tools:
      - web_search_tool             # deep uses advanced web search

Per-Agent Specialization with `exclude_tools`#

Use exclude_tools to remove specific tools from the inherited set. This is useful when different agents need different variants of a tool (e.g., shallow research uses web_search_tool while deep research uses advanced_web_search_tool).

Explicit Override (Backward Compatible)#

If an agent specifies an explicit tools list, it uses exactly those tools and ignores the registry. This preserves backward compatibility with existing configs:

  # Explicit tools list -- registry is NOT used for this agent
  shallow_research_agent:
    _type: shallow_research_agent
    llm: nemotron_llm
    tools:
      - web_search_tool
      - knowledge_search

Adding MCP Tools as Data Sources#

MCP tools (via mcp_client function groups) work with the registry the same way as any other tool. Add the group name to a registry source entry and all agents get it automatically:

# Connect to an external MCP server
function_groups:
  mcp_financial_tools:
    _type: mcp_client
    server:
      transport: streamable-http
      url: ${MCP_SERVER_URL:-http://localhost:9901/mcp}

functions:
  data_sources:
    _type: data_source_registry
    sources:
      - id: web_search
        name: "Web Search"
        tools:
          - web_search_tool
          - advanced_web_search_tool
      - id: knowledge_layer
        name: "Knowledge Base"
        tools:
          - knowledge_search
      - id: financial_data
        name: "Financial Data"
        description: "Query financial reports and market data via MCP."
        tools:
          - mcp_financial_tools         # function group name

That’s it – one registry entry. Every agent automatically gets the MCP tools. The UI shows a “Financial Data” toggle. Per-request data_sources filtering works.

The registry auto-detects that mcp_financial_tools is a function group and uses NAT’s group separator (__) for prefix matching. All tools exposed by the MCP server (e.g., mcp_financial_tools__get_stock_quote, mcp_financial_tools__get_earnings) map to the financial_data data source.

For details on MCP server setup, transport options, tool overrides, and prompt tuning, see MCP Tools.

Disabling a Tool#

To disable a tool (for example, to avoid API usage or restrict agents to specific sources), remove it from the data_source_registry:

functions:
  data_sources:
    _type: data_source_registry
    sources:
      - id: web_search
        name: "Web Search"
        tools:
          - web_search_tool
          - advanced_web_search_tool
      # paper_search removed -- no agent will receive it

Since agents inherit from the registry, removing a tool from the registry removes it from all agents. No per-agent config changes needed.

Optionally comment out or remove the tool’s function definition in functions so the config is clearer.

Adding New Tools or Data Sources#

For guidance on implementing and registering new tools or data sources, refer to:

Adding a Tool – How to create and register a new tool with the NeMo Agent Toolkit.
Adding a Data Source – How to add a new data source, register it with the data source registry, and use MCP tools as data sources.