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wf_mcp Capability Sources

wf_mcp should model capabilities before it models MCP server tool lists. Tools, workflow node specs, prompts, resources, and admin controls all belong to a source. The MCP server, workflow planning, and future UI surfaces are projections of those sources.

If you need the practical "which thing do I call?" view before the domain model, start with wf_mcp_operator_manual.md.

This avoids the current trap where broker admin tools, proxy admin tools, workflow node specs, and upstream MCP tools all look like unrelated systems.

Core Model

A capability source is a named provider of one or more capability kinds. The domain model lives in wf_platform.sources; wf_mcp projects MCP-backed connections into that model rather than owning the model itself.

CapabilitySource
  id: "wf.std" | "wf.docs" | "wf.admin" | "<server>.<account>"
  kind: "system" | "connection"
  enabled: bool
  visibility:
    planner: bool
    mcp_client: bool
    admin_dashboard: bool
  permissions:
    safe_for_workflow: bool
    calls_upstream: bool
    mutates_config: bool
    mutates_auth: bool
  capabilities:
    tools
    node_specs
    reducers
    prompts
    resources

Important rule: a source is not "an MCP tool source." A source owns capabilities. Each surface decides which capability kinds it projects.

For the distinction between raw capabilities, workflow-facing NodeSpecs, and future saved wrapper artifacts, see workflow_capabilities.md.

Canonical Sources

wf.docs

Local platform documentation.

  • Planner-visible: no.
  • MCP-client-visible: yes.
  • Admin-dashboard-visible: yes.
  • MCP tools: none.
  • Workflow safety: not applicable; it owns docs, not workflow nodes.

Current capabilities:

  • prompts: wf.docs.operator_guide, wf.docs.workflow_authoring_guide, wf.docs.troubleshooting_guide.
  • resources: wf://docs/operator-manual, wf://docs/end-to-end-runbook, wf://docs/troubleshooting.

The documentation resource model lives in wf_platform, not in the MCP projection layer. That lets the same manuals feed MCP resources now and other surfaces such as a future CLI or UI later.

wf.std

Workflow standard library.

  • Planner-visible: yes, for reusable workflow node specs.
  • MCP-client-visible: yes, for prompts/resources/manuals.
  • Admin-dashboard-visible: yes, for inspection and source toggling.
  • MCP tools: normally none.
  • Workflow safety: yes.

Expected capabilities:

  • node_specs: wf.std.runtime_error, wf.std.coalesce, wf.std.default_if_none, wf.std.constant, wf.std.pick_key, wf.std.truthy, wf.std.first_item, wf.std.first_item_maybe, wf.std.first_item_or_none, wf.std.last_item, wf.std.last_item_or_none, wf.std.length, wf.std.is_empty.
  • reducers: wf.std.replace, wf.std.append, wf.std.max, wf.std.merge_object, wf.std.set_union.
  • prompts: workflow authoring guide, error-handling guide, mapping guide.
  • resources: reference docs for stdlib node behavior.

wf.mcp

Reserved for future workflow-safe MCP helpers.

wf.mcp currently owns no public NodeSpecs. The previous raw wf.mcp.call_tool helper was deleted because it duplicated the proxy tool surface and used the wrong abstraction for stateful servers. Workflow authors should use generated connection NodeSpecs, saved wrappers, or wf.workflow.call_capability when they need to test a workflow-facing capability.

wf.admin

Human/control-plane administration source.

  • Planner-visible: no by default.
  • MCP-client-visible: no by default.
  • Admin-dashboard-visible: yes.
  • MCP tools: only when explicitly launched with admin exposure enabled.
  • Workflow safety: no.

Expected capabilities:

  • tools: list sources, enable source, disable source, refresh catalog, list connections, add/update/remove connections, view config, reload config, inspect events, and inspect proxy tools.
  • prompts/resources: admin documentation may be useful later.

This source is privileged. A normal client LLM should not automatically see tools that can mutate config, auth, or its own available capability set.

Connection Sources

Each upstream MCP connection is a source, for example everything.default or fixture.personal.

  • Planner-visible: yes when enabled and allowed.
  • MCP-client-visible: yes when enabled and allowed.
  • Admin-dashboard-visible: yes.
  • MCP tools/resources/prompts: discovered from upstream.
  • Workflow node specs: generated wrappers around upstream tools.

Connection sources are the only sources that represent upstream MCP server snapshots. System sources are local broker capabilities.

A configured connection should still appear as a connection source even when no catalog snapshot has been loaded yet. In that state the source can have zero owned capabilities and a description such as No catalog loaded for ...; the absence of discovered capabilities must not make the configured connection disappear from source inventory.

Connection discovery treats tools/list as the required workflow-facing family. Optional MCP families such as resources/list and prompts/list may be absent; servers that return MCP Method not found for those methods still refresh as tool-only sources instead of failing the whole catalog refresh.

Projections

Planner Catalog

The planner catalog shows node_specs where:

source.enabled
and source.visibility.planner
and capability is safe or explicitly allowed for workflow

Examples:

  • include wf.std.runtime_error
  • include everything.default.echo
  • exclude wf.admin.disable_source

MCP Client Tools

The MCP tools/list projection shows tools where:

source.enabled
and source.visibility.mcp_client
and capability kind == tool

Normal mode should not expose wf.admin tools. Admin mode may expose them with clear names such as wf.admin.list_sources.

MCP Client Prompts And Resources

The MCP prompts/list and resources/list projections may show documentation from system sources.

Examples:

  • wf.std.workflow_manual
  • wf.std.error_handling_guide
  • MCP workflow guides under wf.docs

These are MCP-visible without implying the source exposes MCP tools.

Admin Dashboard

The admin dashboard projection shows sources, visibility, health, auth status, and privileged operations.

This is the preferred place for source toggling:

  • disable an entire source
  • enable an entire source
  • refresh a source catalog
  • update connection config
  • log out / replace auth

Dashboard operations should use wf.admin capability definitions or Python control APIs, not ad hoc tool functions copied across broker and proxy modes.

Implemented Shape

The code now has the first capability-source layer in place.

  • wf_platform.CapabilitySource owns source metadata, visibility, permissions, and capability buckets.
  • CapabilitySource is the mutable runtime registry object; typed SourceStatus and SourceInventory snapshots are the serializable domain projections used at boundaries such as list_sources().
  • Executable NodeSpec objects stay inside runtime buckets because they hold Python callables. Inventory exposes NodeSpecInventory contracts instead: names, descriptions, outcomes, schemas, and execution flags, but never the wrapped function object itself.
  • Reducer inventory follows the same rule: executable reducer definitions stay private, while ReducerInventory exposes only reducer names, descriptions, and config schemas.
  • WfMcpService.capability_sources is the canonical in-memory registry.
  • Planner node lookup reads CapabilitySource.capabilities.node_specs directly; the old SpecSource compatibility layer has been removed.
  • wf.std owns current wf_authoring.ops workflow node specs under wf.std.*.
  • wf.mcp is reserved for future workflow-safe MCP helpers and currently owns no public NodeSpecs.
  • wf.admin owns privileged admin capability metadata and is not planner-visible by default.
  • Transparent proxy admin tools now use dotted wf.admin.* names through LdaNamespace.
  • wf.admin and wf.mcp are reserved connection ids.
  • Planner catalog, list_available_specs(), and workflow spec resolution respect source enabled and visibility.planner.

Legacy broker MCP tools still expose compatibility names such as list_connections and get_planner_catalog on the compatibility-only broker server constructor. They now reuse the same service-admin registrar as the public server, with only the visible names changed. The public server projects service-backed admin tools such as wf.admin.list_sources alongside proxy-backed admin tools under the same wf.admin.* namespace.

Current Code Mapping

Current code has several useful pieces but the boundaries are blurred.

Current location Current role Target source
wf_authoring.ops reusable workflow node specs wf.std.node_specs
wf_core built-in reducers reusable workflow state reducers wf.std.reducers
wf_mcp.broker.service.builtins local workflow specs wf.std
wf_mcp.broker.tools compatibility wrapper over shared service-admin registration wf.admin.tools
wf_mcp.admin_surface.tools shared service-backed admin tool registration wf.admin.tools
wf_mcp.proxy.admin proxy-backed public admin tools wf.admin.tools
discovered MCP tools upstream tools and workflow wrappers connection source
broker resources/prompts catalog/status/planning context likely wf.admin or docs sources

New source behavior should be added to CapabilitySource.

Naming Rules

Use source ids consistently:

  • wf.std.* for workflow standard library capabilities.
  • wf.mcp.* for workflow MCP runtime helpers.
  • wf.admin.* for privileged control/admin capabilities.
  • <connection_id>.* for upstream connection capabilities.

Avoid using wf.mcp_* for admin tools. wf.mcp is reserved for workflow MCP runtime helpers. Transparent proxy admin tools now use dotted wf.admin.* names.

Migration Path

  1. Keep explicit admin MCP exposure controls on the server surface.
  2. Project admin tools from wf.admin only when admin MCP exposure is enabled.
  3. Add source-level enable/disable operations backed by wf.admin.
  4. Add persisted source policy so source visibility survives process restart.
  5. Add system prompts/resources for wf.std and wf.mcp manuals.

The implementation should avoid having separate backend layers define copies of the same admin/control capabilities.

Current Inventory Surface

list_sources() is the compact source-discovery surface:

  • returns paged source summaries with visibility, permissions, and counts
  • includes small sorted preview name lists per capability kind
  • includes has_more flags when a preview omits additional owned names
  • is intentionally compact enough for progressive discovery
  • pairs with inspect_source(source_id) for the full owned-capability inventory

Humans and LLM authoring clients should list sources first, then inspect only the sources they need. Planner projection remains a different use of source metadata, not a second source model.

The summary payload intentionally does not include schemas or executable contracts:

{
  "id": "wf.std",
  "node_spec_count": 12,
  "reducer_count": 6,
  "preview": {
    "node_specs": [
      "wf.std.coalesce",
      "wf.std.constant",
      "wf.std.default_if_none"
    ],
    "reducers": ["wf.std.add", "wf.std.append", "wf.std.max"]
  },
  "has_more": {
    "node_specs": true,
    "reducers": true
  }
}

Call inspect_source("wf.std") only when those previews indicate the source is relevant. That keeps large source inventories usable for MCP clients with tight context windows.

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