Hosted MCP access to Natural payment operations for Vellum assistants.
Vellum plugin for Natural's hosted Model Context Protocol (MCP) server.
assistant plugins install natural
This is the install command, resolving the plugin by name from the Vellum marketplace catalog. It works once the plugin has been published there, which is a reviewed step.
Then authorize the Natural MCP server through your client's connection settings.
assistant plugins install https://github.com/vellum-ai/natural
Installing by URL is for QA: it is how a version gets exercised on a real assistant before it is published for review. It clones this tree verbatim and bypasses the catalog, so the source is untrusted and the CLI prints a warning naming it. Point it at a branch or a fork to test a change that is not on main yet.
Use the name, not the URL, once the plugin is published.
Use a Natural agent key for this connector. Agent keys bind actions to one Natural agent, so Natural attributes activity to that agent instead of only to the user account. Do not use OAuth or a regular party API key for this integration.
Setup is driven by the skill script skills/natural/scripts/natural_setup.ts, run with Bun, not by a host tool. When Natural is unauthenticated, the assistant runs:
bun skills/natural/scripts/natural_setup.ts start
That prints the onboarding steps and makes a best-effort attempt to open natural.com using whatever URL opener the machine provides ($BROWSER, xdg-open, open, wslview). It assumes no particular browser tooling: if nothing can open a URL, it says so and the assistant or the user opens the link instead. At natural.com:
Only after the user confirms they have returned with the agent key ready may the assistant run:
bun skills/natural/scripts/natural_setup.ts prompt --onboarding-complete
The script refuses to reach this phase before start has run, and refuses without the explicit --onboarding-complete confirmation. It then opens the host's secure credential prompt for service natural, field api_key. Where the host offers no such prompt, the script stores nothing and explains that the user must save the key in host credential storage under that same identity.
Never paste the key into chat, script arguments, source control, mcp.json, or a normal message. The key is used as a bearer token against https://mcp.natural.com and is stored only in host-managed credential storage.
The Vellum host injects the agent key securely. Keep the secret in host-managed credential storage. Never add it to mcp.json, source files, README examples, logs, or committed configuration.
Read the bundled skills/natural/SKILL.md before using payment-related tools. Treat transfers, withdrawals, deposits, fulfillment, and other state-changing operations as consequential actions requiring explicit confirmation immediately before execution.