POST Submit MCP JSON-RPC

{
  "id": "demo",
  "jsonrpc": "2.0"
}

{
  "code": "demo",
  "detail": "Demo error detail; inspect the documented code.",
  "instance": "demo",
  "message": "Demo error detail; inspect the documented code.",
  "message_key": "errors.requestFailed",
  "message_params": {},
  "request_id": "00000000000000000000000000000000",
  "status": 400,
  "title": "Demo error",
  "type": "about:blank"
}

{
  "code": "demo",
  "detail": "Demo error detail; inspect the documented code.",
  "instance": "demo",
  "message": "Demo error detail; inspect the documented code.",
  "message_key": "errors.requestFailed",
  "message_params": {},
  "request_id": "00000000000000000000000000000000",
  "status": 401,
  "title": "Demo error",
  "type": "about:blank"
}

{
  "code": "demo",
  "detail": "Demo error detail; inspect the documented code.",
  "instance": "demo",
  "message": "Demo error detail; inspect the documented code.",
  "message_key": "errors.requestFailed",
  "message_params": {},
  "request_id": "00000000000000000000000000000000",
  "status": 403,
  "title": "Demo error",
  "type": "about:blank"
}

{
  "code": "demo",
  "detail": "Demo error detail; inspect the documented code.",
  "instance": "demo",
  "message": "Demo error detail; inspect the documented code.",
  "message_key": "errors.requestFailed",
  "message_params": {},
  "request_id": "00000000000000000000000000000000",
  "status": 413,
  "title": "Demo error",
  "type": "about:blank"
}

{
  "code": "demo",
  "detail": "Demo error detail; inspect the documented code.",
  "instance": "demo",
  "message": "Demo error detail; inspect the documented code.",
  "message_key": "errors.requestFailed",
  "message_params": {},
  "request_id": "00000000000000000000000000000000",
  "status": 415,
  "title": "Demo error",
  "type": "about:blank"
}

{
  "code": "demo",
  "detail": "Demo error detail; inspect the documented code.",
  "instance": "demo",
  "message": "Demo error detail; inspect the documented code.",
  "message_key": "errors.requestFailed",
  "message_params": {},
  "request_id": "00000000000000000000000000000000",
  "status": 503,
  "title": "Demo error",
  "type": "about:blank"
}

curl --silent --show-error --output /dev/null --write-out "%{http_code}\n" \
  --request POST \
  --header @"$HOME/.config/metribeacon/headers.txt" \
  --header "Content-Type: application/json" \
  --header "Accept: application/json, text/event-stream" \
  --data-binary '{"jsonrpc":"2.0","id":1,"method":"initialize","params":{"protocolVersion":"2025-06-18","capabilities":{},"clientInfo":{"name":"demo-client","version":"1.0.0"}}}' \
  "https://metribeacon.com/mcp"

import json
from pathlib import Path
from urllib.request import Request, HTTPRedirectHandler, build_opener
from urllib.error import HTTPError

headers = json.loads((Path.home() / ".config/metribeacon/headers.json").read_text())
headers["Content-Type"] = "application/json"
headers["Accept"] = "application/json, text/event-stream"
request = Request("https://metribeacon.com/mcp", data="{\"jsonrpc\":\"2.0\",\"id\":1,\"method\":\"initialize\",\"params\":{\"protocolVersion\":\"2025-06-18\",\"capabilities\":{},\"clientInfo\":{\"name\":\"demo-client\",\"version\":\"1.0.0\"}}}".encode("utf-8"), headers=headers, method="POST")
class NoRedirect(HTTPRedirectHandler):
    def redirect_request(self, request, fp, code, message, headers, target):
        return None

opener = build_opener(NoRedirect())
try:
    with opener.open(request, timeout=10) as response:
        print(response.status)
except HTTPError as error:
    print(error.code)
    error.close()

import { readFile } from "node:fs/promises";
import { homedir } from "node:os";
import { join } from "node:path";

const headers = JSON.parse(await readFile(join(homedir(), ".config/metribeacon/headers.json"), "utf8"));
headers["Content-Type"] = "application/json";
headers["Accept"] = "application/json, text/event-stream";
const response = await fetch("https://metribeacon.com/mcp", {
  method: "POST", headers, redirect: "manual",
  signal: AbortSignal.timeout(10000), body: "{\"jsonrpc\":\"2.0\",\"id\":1,\"method\":\"initialize\",\"params\":{\"protocolVersion\":\"2025-06-18\",\"capabilities\":{},\"clientInfo\":{\"name\":\"demo-client\",\"version\":\"1.0.0\"}}}",
});
console.log(response.status);
await response.body?.cancel();

package main

import (
  "fmt"
  "net/http"
  "time"
  "encoding/json"
  "os"
  "path/filepath"
  "strings"
)

func main() {
  home, err := os.UserHomeDir(); if err != nil { panic("request failed; credentials and response omitted") }
  raw, err := os.ReadFile(filepath.Join(home, ".config/metribeacon/headers.json")); if err != nil { panic("request failed; credentials and response omitted") }
  var headers map[string]string
  if json.Unmarshal(raw, &headers) != nil { panic("invalid local headers") }
  request, err := http.NewRequest("POST", "https://metribeacon.com/mcp", strings.NewReader("{\"jsonrpc\":\"2.0\",\"id\":1,\"method\":\"initialize\",\"params\":{\"protocolVersion\":\"2025-06-18\",\"capabilities\":{},\"clientInfo\":{\"name\":\"demo-client\",\"version\":\"1.0.0\"}}}"))
  if err != nil { panic("request failed; credentials and response omitted") }
  for name, value := range headers { request.Header.Set(name, value) }
  request.Header.Set("Content-Type", "application/json")
  request.Header.Set("Accept", "application/json, text/event-stream")
  client := &http.Client{Timeout: 10*time.Second, CheckRedirect: func(*http.Request, []*http.Request) error { return http.ErrUseLastResponse }}
  response, err := client.Do(request)
  if err != nil { panic("request failed; credentials and response omitted") }
  defer response.Body.Close()
  fmt.Println(response.StatusCode)
}