Compose an MCP¶

A composite is a curated MCP surface: pick a handful of tools from one or more upstream MCP servers, optionally embed registered workflow manifests, attach a system prompt, and serve the whole thing as one named MCP. Composites are stored in daas.db and served in-proc by the consolidated fd-daas-mcp server.

This page is the authoring flow: manifest format → tool selection → workflow embedding → prompt → run. For the per-tool reference see Tool Groups. For a guided scaffold, use the fd-coding-mcp-creator skill.

The manifest format¶

A composite manifest (written by composite_create_manifest) is a JSON object:

{
  "name": "macro-analyst",
  "description": "macro data fetch + indicators, scoped to sovereign series",
  "upstreams": [
    {"key": "data", "transport": "http", "url": "http://127.0.0.1:8300"}
  ],
  "tools": [
    {"upstream": "data", "tool": "read"}
  ],
  "workflows": ["data-fetch", "indicators"],
  "prompt": "You are a macro-data analyst. Only fetch sovereign and central-bank series..."
}

Field	Purpose
`name`	Unique composite name; used as `COMPOSITE=<name>` to serve it.
`description`	Optional human-readable label.
`upstreams`	MCP servers the composite proxies. `key` is the mount namespace (served tools become `<key>_<tool>`). `transport` = `http` (needs `url`) or `stdio` (needs `command`/`args`/`env`/`cwd`). The canonical upstream is `fd-open-data-mcp` over HTTP at `http://127.0.0.1:8300`.
`tools`	List of `{upstream: <key>, tool: <name>}`. Each is proxied and served as `<key>_<tool>`.
`workflows`	Names of registered workflow manifests (rows in the `workflows` table, registered via `workflow_register`). Each surfaces as a lazy tool that runs the workflow engine on call.
`prompt`	System prompt applied to the composite's FastMCP surface.

Authoring flow¶

1. Pick upstreams¶

Almost always just fd-open-data-mcp (HTTP @ :8300, key data). It covers all data fetch. Add a second upstream only when you need a server the data layer doesn't already front.

2. Select tools¶

List what an upstream exposes, then pick the few you want:

composite_list_available_tools(composite="macro-analyst", upstream_key="data")
composite_add_tool(composite="macro-analyst", upstream_key="data", tool_name="read")

Or, in manifest mode, pass the whole set at once:

composite_create_manifest(
    name="macro-analyst",
    upstreams=[{"key": "data", "transport": "http", "url": "http://127.0.0.1:8300"}],
    tools=[{"upstream": "data", "tool": "read"}],
)

3. Embed workflows¶

Embed a registered workflow so callers can trigger a multi-step fetch without remembering the steps. List registered workflows with workflow_list(), then pass their names in workflows:

composite_create_manifest(..., workflows=["data-fetch", "indicators"])

Each name becomes a lazy tool on the composite — calling it runs the workflow engine with the params you pass.

4. Attach a prompt¶

A short system prompt scopes the serving agent. Keep it brief — a scope beats a playbook:

composite_create_manifest(..., prompt="You are a macro-data analyst. Only fetch sovereign and central-bank series.")

5. Serve¶

COMPOSITE=macro-analyst fd-daas-mcp/bin/fd-daas-mcp-server

The served surface exposes: each selected tool (as <key>_<tool>), each embedded workflow (as its own tool), plus the management tools — all behind the system prompt.

Maintenance¶

Update — composite_update_manifest(name, ...); note upstreams/tools replace the existing sets wholesale when given.
List — composite_list_manifests().
Delete — composite_delete_manifest(name) (cascades upstreams/tools/chains).

Principles¶

Curate, don't create. A composite selects existing tools/workflows; it never invents new ones. If a needed tool doesn't exist, build the upstream first (fd-coding-daas-datasource-builder) or register a workflow (workflow_register).
One upstream by default. fd-open-data-mcp covers all data fetch.
Prompt is scope, not script. A short bound beats a long playbook.