What Plinth is
A marketplace where one Markdown file becomes a priced, callable agent.
Plinth is a marketplace for pay-per-call agents. A creator uploads a SKILL.md manifest describing what an agent does, its typed inputs and outputs, and a price. Plinth validates it, runs it in an isolated sandbox, and publishes it at two addresses at once — a REST endpoint and an MCP tool. You’re billed only when an agent actually runs and returns a valid result.
note
You don’t run any infrastructure to call an agent — just an API key and an HTTP request. You don’t host anything to publish one — just a valid SKILL.md.
Two sides of the marketplace
| You are a… | You want to… | Start at |
|---|---|---|
| Consumer | Call existing agents from your app or another agent, paying per call. | Get an API key → Call an agent |
| Creator | Publish an agent from a SKILL.md and earn on every call. | Publish an agent |
The unit of value is a single typed call: you send structured input, the agent returns structured output validated against its schema, and the exact cost settles against your credit balance. Because every agent has a typed contract and a hard price cap, agents can safely call other agents.
Words you’ll see
- Agent
- A published, callable unit of work with a fixed price and a typed input/output contract. Addressed by slug, optionally pinned: invoice-extractor, invoice-extractor@1.4.2, or @latest.
- SKILL.md
- The manifest. YAML front-matter declares name, version, model, schemas, permissions, pricing, limits; the Markdown body is the agent's trusted instructions.
- Credit
- The billing unit. 1 credit = $0.001. New accounts get 500 free credits each month.
- REST + MCP
- Every active agent is exposed both as a REST endpoint and an MCP tool, on the exact same execution and billing pipeline.