Mcp

An MCP server as a tool source, reached over Streamable HTTP with an HTTP client the caller has already given the credentials the server asks for, so no credential enters this package. The source asks the server for its tools and runs them, and nothing else of MCP: resources, prompts, and the requests a server makes of its client are left out.

How the server is spoken to, statelessly or with a session, is the transport’s to settle. The source adds what only tools have: the headers that mirror the parameters a tool marks.

Since v0.1.0

Constructors

http

Makes a source of the tools of the MCP server at options.url. Making it contacts nothing: the server is first reached when the source lists or runs its tools. A tool that reports isError fails as CallFailedError, with what it said, and one that asks for input first as UnsupportedError.

Example (A source of an MCP server, with the server’s credentials on the client)

import { Mcp } from "@amends-dev/toolkit"
import { Config, Effect, Redacted } from "effect"
import { FetchHttpClient, HttpClient, HttpClientRequest } from "effect/http"

const program = Effect.gen(function* () {
  const token = yield* Config.Redacted("MCP_TOKEN")
  // The client carries the credentials, so the source never sees them.
  const client = (yield* HttpClient.HttpClient).pipe(
    HttpClient.mapRequest(HttpClientRequest.bearerToken(Redacted.value(token)))
  )
  const tasks = yield* Mcp.http({ name: "tasks", url: "https://mcp.example.com/mcp", client })
  // The server is first reached here: the catalog stores what it lists.
  const definitions = yield* tasks.discover
  const result = yield* tasks.call("list_tasks", { status: "open" })
  return { definitions, result }
}).pipe(Effect.provide(FetchHttpClient.layer))

Signature

declare const http: (options: Transport.Options) => Effect.Effect<ToolSource.ToolSource, never, never>

Source

Since v0.1.0

Options

Options

What http takes: the source’s name, the server’s address, the client that sends its requests with the server’s credentials, and how long a request may take.

Signature

declare const Options: Transport.Options

Source

Since v0.1.0