feat: support MCP bridge (#140)

.gitignore

@@ -15,3 +15,4 @@ node_modules
 /package.json
 package-lock.json
 *.lock
+/mcp.json

Argcfile.sh

@@ -2,7 +2,7 @@
 set -e
 
 BIN_DIR=bin
-TMP_DIR="cache/tmp"
+TMP_DIR="cache/__tmp__"
 VENV_DIR=".venv"
 
 LANG_CMDS=( \
@@ -421,9 +421,8 @@ test-demo@tool() {
 # @cmd Test agents
 # @alias agent:test
 test@agent() {
-    tmp_dir="cache/tmp"
-    mkdir -p "$tmp_dir"
-    names_file="$tmp_dir/agents.txt"
+    mkdir -p "$TMP_DIR"
+    names_file="$TMP_DIR/agents.txt"
     argc list@agent > "$names_file"
     argc build@agent --names-file "$names_file"
     test-demo@agent
@@ -499,6 +498,12 @@ install() {
     fi
 }
 
+# @cmd Run mcp command
+# @arg args~[?`_choice_mcp_args`] The mcp command and arguments
+mcp() {
+    bash ./scripts/mcp.sh "$@"
+}
+
 # @cmd Create a boilplate tool script
 # @alias tool:create
 # @arg args~
@@ -671,6 +676,16 @@ _choice_agent_action() {
     argc generate-declarations@agent "$1" --oneline | sed "$expr"
 }
 
+_choice_mcp_args() {
+    if [[ "$ARGC_COMPGEN" -eq 1 ]]; then
+        args=( "${argc__positionals[@]}" )
+        args[-1]="$ARGC_LAST_ARG"
+        argc --argc-compgen generic scripts/mcp.sh mcp "${args[@]}"
+    else
+        :;
+    fi
+}
+
 _die() {
     echo "$*" >&2
     exit 1

mcp/bridge/README.md

@@ -0,0 +1,42 @@
+# MCP-Bridge
+
+Let MCP tools be used by LLM functions.
+
+## Get Started
+
+1. Create a `mpc.json` at `<llm-functions-dir>`.
+
+```json
+{
+  "mcpServers": {
+    "sqlite": {
+      "command": "uvx",
+      "args": [
+        "mcp-server-sqlite",
+        "--db-path",
+        "/tmp/foo.db"
+      ]
+    },
+    "github": {
+      "command": "npx",
+      "args": [
+        "-y",
+        "@modelcontextprotocol/server-github"
+      ],
+      "env": {
+        "GITHUB_PERSONAL_ACCESS_TOKEN": "<YOUR_TOKEN>"
+      }
+    }
+  }
+}
+```
+
+> MCP-Bridge will launch the server and register all the tools listed by the server. The tool identifier will be `server_toolname` to avoid clashes.
+
+2. Run the bridge server, build mcp tool binaries, update functions.json, all with:
+
+```
+argc mcp start
+```
+
+> Run `argc mcp stop` to stop the bridge server, recover functions.json

mcp/bridge/index.js

@@ -0,0 +1,195 @@
+#!/usr/bin/env node
+
+import * as path from "node:path";
+import * as fs from "node:fs";
+import { Client } from "@modelcontextprotocol/sdk/client/index.js";
+import { StdioClientTransport } from "@modelcontextprotocol/sdk/client/stdio.js";
+import express from "express";
+
+const app = express();
+const PORT = process.env.MCP_BRIDGE_PORT || 8808;
+
+let [rootDir] = process.argv.slice(2);
+
+if (!rootDir) {
+  console.error("Usage: mcp-bridge <llm-functions-dir>");
+  process.exit(1);
+}
+
+let mcpServers = {};
+const mcpJsonPath = path.join(rootDir, "mcp.json");
+try {
+  const data = await fs.promises.readFile(mcpJsonPath, "utf8");
+  mcpServers = JSON.parse(data)?.mcpServers;
+} catch {
+  console.error(`Failed to read json at '${mcpJsonPath}'`);
+  process.exit(1);
+}
+
+async function startMcpServer(id, serverConfig) {
+  console.log(`Starting ${id} server...`);
+  const capabilities = { tools: {} };
+  const transport = new StdioClientTransport({
+    ...serverConfig,
+  });
+  const client = new Client(
+    { name: id, version: "1.0.0" },
+    { capabilities }
+  );
+  await client.connect(transport);
+  const { tools: toolDefinitions } = await client.listTools()
+  const tools = toolDefinitions.map(
+    ({ name, description, inputSchema }) =>
+    ({
+      spec: {
+        name: `${normalizeToolName(`${id}_${name}`)}`,
+        description,
+        parameters: inputSchema,
+      },
+      impl: async args => {
+        const res = await client.callTool({
+          name: name,
+          arguments: args,
+        });
+        const content = res.content;
+        let text = arrayify(content)?.map(c => {
+          switch (c.type) {
+            case "text":
+              return c.text || ""
+            case "image":
+              return c.data
+            case "resource":
+              return c.resource?.uri || ""
+            default:
+              return c
+          }
+        }).join("\n");
+        if (res.isError) {
+          text = `Tool Error\n${text}`;
+        }
+        return text;
+      },
+    })
+  );
+  return {
+    tools,
+    [Symbol.asyncDispose]: async () => {
+      try {
+        console.log(`Closing ${id} server...`);
+        await client.close();
+        await transport.close();
+      } catch { }
+    },
+  }
+}
+
+async function runBridge() {
+  let hasError = false;
+  let runningMcpServers = await Promise.all(
+    Object.entries(mcpServers).map(
+      async ([name, serverConfig]) => {
+        try {
+          return await startMcpServer(name, serverConfig)
+        } catch (err) {
+          hasError = true;
+          console.error(`Failed to start ${name} server; ${err.message}`)
+        }
+      }
+    )
+  );
+  runningMcpServers = runningMcpServers.filter(s => !!s);
+  const stopMcpServers = () => Promise.all(runningMcpServers.map(s => s[Symbol.asyncDispose]()));
+  if (hasError) {
+    await stopMcpServers();
+    return;
+  }
+
+  const definitions = runningMcpServers.flatMap(s => s.tools.map(t => t.spec));
+  const runTool = async (name, args) => {
+    for (const server of runningMcpServers) {
+      const tool = server.tools.find(t => t.spec.name === name);
+      if (tool) {
+        return tool.impl(args);
+      }
+    }
+    return `Not found tool '${name}'`;
+  };
+
+  app.use((err, _req, res, _next) => {
+    res.status(500).send(err?.message || err);
+  });
+
+  app.use(express.json());
+
+  app.get("/", (_req, res) => {
+    res.send(`# MCP Bridge API
+  
+- POST /tools/:name 
+  \`\`\`
+  curl -X POST http://localhost:8808/tools/filesystem_write_file  \\
+    -H 'content-type: application/json' \\
+    -d '{"path": "/tmp/file1", "content": "hello world"}'
+  \`\`\`
+- GET /tools
+  \`\`\`
+  curl http://localhost:8808/tools
+  \`\`\`
+  `);
+  });
+
+  app.get("/tools", (_req, res) => {
+    res.json(definitions);
+  });
+
+  app.post("/tools/:name", async (req, res) => {
+    try {
+      const output = await runTool(req.params.name, req.body);
+      res.send(output);
+    } catch (err) {
+      res.status(500).send(err);
+    }
+  });
+
+  app.get("/pid", (_req, res) => {
+    res.send(process.pid.toString());
+  });
+
+  app.get("/health", (_req, res) => {
+    res.send("OK");
+  });
+
+  app.use((_req, res, _next) => {
+    res.status(404).send("Not found");
+  });
+
+  const server = app.listen(PORT, () => {
+    console.log(`Server is running on port ${PORT}`);
+  });
+
+  return async () => {
+    server.close(() => console.log("Http server closed"));
+    await stopMcpServers();
+  };
+}
+
+function arrayify(a) {
+  let r;
+  if (a === undefined) r = [];
+  else if (Array.isArray(a)) r = a.slice(0);
+  else r = [a];
+
+  return r
+}
+
+function normalizeToolName(name) {
+  return name.toLowerCase().replace(/-/g, "_");
+}
+
+runBridge()
+  .then(stop => {
+    if (stop) {
+      process.on('SIGINT', stop);
+      process.on('SIGTERM', stop);
+    }
+  })
+  .catch(console.error);

mcp/bridge/package.json

@@ -0,0 +1,22 @@
+{
+  "name": "mcp-bridge",
+  "version": "1.0.0",
+  "description": "Let MCP tools be used by LLM functions",
+  "license": "MIT",
+  "author": "sigoden <sigoden@gmail.com>",
+  "homepage": "https://github.com/sigoden/llm-functions/tree/main/mcp/bridge",
+  "repository": {
+    "type": "git",
+    "url": "git+https://github.com/sigoden/llm-functions.git",
+    "directory": "mcp/bridge"
+  },
+  "private": true,
+  "type": "module",
+  "bin": {
+    "mcp-bridge": "index.js"
+  },
+  "dependencies": {
+    "@modelcontextprotocol/sdk": "^1.0.3",
+    "express": "^4.21.2"
+  }
+}

scripts/mcp.sh

@@ -0,0 +1,176 @@
+#!/usr/bin/env bash
+set -e
+
+ROOT_DIR="$(cd -- "$( dirname -- "${BASH_SOURCE[0]}" )/.." &> /dev/null && pwd)"
+BIN_DIR="$ROOT_DIR/bin"
+MCP_DIR="$ROOT_DIR/cache/__mcp__"
+MCP_JSON_PATH="$ROOT_DIR/mcp.json"
+FUNCTIONS_JSON_PATH="$ROOT_DIR/functions.json"
+MCP_BRIDGE_PORT="${MCP_BRIDGE_PORT:-8808}"
+
+# @cmd Start/Restart mcp bridge server
+start() {
+    if [[ ! -f "$MCP_JSON_PATH" ]]; then
+        _die "error: not found mcp.json"
+    fi
+    stop
+    mkdir -p "$MCP_DIR"
+    index_js="$ROOT_DIR/mcp/bridge/index.js"
+    llm_functions_dir="$ROOT_DIR"
+    if _is_win; then
+        index_js="$(cygpath -w "$index_js")"
+        llm_functions_dir="$(cygpath -w "$llm_functions_dir")"
+    fi
+    echo "Run MCP Bridge server"
+    nohup node  "$index_js" "$llm_functions_dir" > "$MCP_DIR/mcp-bridge.log" 2>&1 &
+    wait-for-server
+    echo "Merge MCP tools into functions.json"
+    merge-functions > "$MCP_DIR/functions.json"
+    cp -f "$MCP_DIR/functions.json" "$FUNCTIONS_JSON_PATH"
+    build-bin
+}
+
+# @cmd Stop mcp bridge server
+stop() {
+    pid="$(get-server-pid)"
+    if [[ -n "$pid" ]]; then
+        if _is_win; then
+            taskkill /PID "$pid" /F > /dev/null 2>&1 || true
+        else
+            kill -9 "$pid" > /dev/null 2>&1 || true
+        fi
+    fi
+    mkdir -p "$MCP_DIR"
+    unmerge-functions > "$MCP_DIR/functions.original.json"
+    cp -f "$MCP_DIR/functions.original.json" "$FUNCTIONS_JSON_PATH"
+}
+
+# @cmd Call mcp tool
+# @arg tool![`_choice_tool`] The tool name
+# @arg json The json data
+call() {
+    if [[ -z "$argc_json" ]]; then
+        declaration="$(build-declarations | jq --arg tool "$argc_tool" -r '.[] | select(.name == $tool)')"
+        if [[ -n "$declaration" ]]; then
+            _ask_json_data "$declaration"
+        fi
+    fi
+    if [[ -z "$argc_json" ]]; then
+        _die "error: no JSON data"
+    fi
+    bash "$ROOT_DIR/scripts/run-mcp-tool.sh" "$argc_tool" "$argc_json"
+}
+
+# @cmd Show logs
+# @flag -f --follow Follow mode
+logs() {
+    args=""
+    if [[ -n "$argc_follow" ]]; then
+        args="$args -f"
+    fi
+    if [[ -f "$MCP_DIR/mcp-bridge.log" ]]; then
+        tail $args "$MCP_DIR/mcp-bridge.log"
+    fi
+}
+
+# @cmd Build tools to bin
+build-bin() {
+    tools=( $(build-declarations | jq -r '.[].name') )
+    for tool in "${tools[@]}"; do
+        if _is_win; then
+            bin_file="$BIN_DIR/$tool.cmd"
+            _build_win_shim > "$bin_file"
+        else
+            bin_file="$BIN_DIR/$tool"
+            ln -s -f "$ROOT_DIR/scripts/run-mcp-tool.sh" "$bin_file"
+        fi
+        echo "Build bin/$tool"
+    done
+}
+
+# @cmd Merge mcp tools into functions.json
+merge-functions() {
+    jq --argjson json1 "$(unmerge-functions)" --argjson json2 "$(build-declarations)" -n '($json1 + $json2)'
+}
+
+# @cmd Unmerge mcp tools from functions.json
+unmerge-functions() {
+    functions="[]"
+    if [[ -f  "$FUNCTIONS_JSON_PATH" ]]; then
+        functions="$(cat "$FUNCTIONS_JSON_PATH")"
+    fi
+    printf "%s" "$functions" | jq 'map(select(has("mcp") | not))'
+}
+
+# @cmd Build tools to bin
+build-declarations() {
+    curl -sS http://localhost:$MCP_BRIDGE_PORT/tools | jq '.[] |= . + {mcp: true}'
+}
+
+# @cmd Wait for mcp bridge server to ready
+wait-for-server() {
+    while true; do
+        if [[ "$(curl -fsS http://localhost:$MCP_BRIDGE_PORT/health 2>&1)" == "OK" ]]; then
+            break;
+        fi
+        sleep 1
+    done
+}
+
+# @cmd
+get-server-pid() {
+    curl -fsSL http://localhost:$MCP_BRIDGE_PORT/pid 2>/dev/null || true
+}
+
+_ask_json_data() {
+    declaration="$1"
+    echo 'Missing the JSON data but here are its properties:'
+    echo "$declaration" | ./scripts/declarations-util.sh pretty-print | sed -n '2,$s/^/>/p'
+    echo 'Generate placeholder data:'
+    data="$(echo "$declaration" | _declarations_json_data)"
+    echo ">  $data"
+    read -e -r -p 'JSON data (Press ENTER to use placeholder): ' res
+    if [[ -z "$res" ]]; then
+        argc_json="$data"
+    else
+        argc_json="$res"
+    fi
+}
+
+_declarations_json_data() {
+   ./scripts/declarations-util.sh generate-json | tail -n +2
+}
+
+_build_win_shim() {
+    run="\"$(argc --argc-shell-path)\" --noprofile --norc"
+    cat <<-EOF
+@echo off
+setlocal
+
+set "bin_dir=%~dp0"
+for %%i in ("%bin_dir:~0,-1%") do set "script_dir=%%~dpi"
+set "script_name=%~n0"
+
+$run "%script_dir%scripts\run-mcp-tool.sh" "%script_name%" %*
+EOF
+}
+
+_is_win() {
+    if [[ "$OS" == "Windows_NT" ]]; then
+        return 0
+    else
+        return 1
+    fi
+}
+
+_choice_tool() {
+    build-declarations | jq -r '.[].name'
+}
+
+_die() {
+    echo "$*" >&2
+    exit 1
+}
+
+# See more details at https://github.com/sigoden/argc
+eval "$(argc --argc-eval "$0" "$@")"

scripts/run-mcp-tool.sh

@@ -0,0 +1,93 @@
+#!/usr/bin/env bash
+set -e
+
+main() {
+    root_dir="$(cd -- "$( dirname -- "${BASH_SOURCE[0]}" )/.." &> /dev/null && pwd)"
+    self_name=run-mcp-tool.sh
+    parse_argv "$@"
+    load_env "$root_dir/.env" 
+    run
+}
+
+parse_argv() {
+    if [[ "$0" == *"$self_name" ]]; then
+        tool_name="$1"
+        tool_data="$2"
+    else
+        tool_name="$(basename "$0")"
+        tool_data="$1"
+    fi
+    if [[ "$tool_name" == *.sh ]]; then
+        tool_name="${tool_name:0:$((${#tool_name}-3))}"
+    fi
+    if [[ -z "$tool_data" ]] || [[ -z "$tool_name" ]]; then
+        die "usage: ./run-tool.sh <tool-name> <tool-data>"
+    fi
+}
+
+
+load_env() {
+    local env_file="$1" env_vars
+    if [[ -f "$env_file" ]]; then
+        while IFS='=' read -r key value; do
+            if [[ "$key" == $'#'* ]] || [[ -z "$key" ]]; then
+                continue
+            fi
+            if [[ -z "${!key+x}" ]]; then
+                env_vars="$env_vars $key=$value"
+            fi
+        done < <(cat "$env_file"; echo "")
+        if [[ -n "$env_vars" ]]; then
+            eval "export $env_vars"
+        fi
+    fi
+}
+
+run() {
+    no_llm_output=0
+    if [[ -z "$LLM_OUTPUT" ]]; then
+        no_llm_output=1
+        export LLM_OUTPUT="$(mktemp)"
+    fi
+    curl -sS "http://localhost:${MCP_BRIDGE_PORT:-8808}/tools/$tool_name" \
+        -X POST \
+        -H 'content-type: application/json' \
+        -d "$tool_data" > "$LLM_OUTPUT"
+
+    if [[ "$no_llm_output" -eq 1 ]]; then
+        cat "$LLM_OUTPUT"
+    else
+        dump_result
+    fi
+}
+
+dump_result() {
+    if [ ! -t 1 ]; then
+        return;
+    fi
+    
+    local agent_env_name agent_env_value func_env_name func_env_value show_result=0
+    agent_env_name="LLM_AGENT_DUMP_RESULT_$(echo "$LLM_AGENT_NAME" | tr '[:lower:]' '[:upper:]' | tr '-' '_')"
+    agent_env_value="${!agent_env_name:-"$LLM_AGENT_DUMP_RESULT"}"
+    func_env_name="${agent_env_name}_$(echo "$LLM_AGENT_FUNC" | tr '[:lower:]' '[:upper:]' | tr '-' '_')"
+    func_env_value="${!func_env_name}"
+    if [[ "$agent_env_value" == "1" || "$agent_env_value" == "true" ]]; then
+        if [[ "$func_env_value" != "0" && "$func_env_value" != "false" ]]; then
+            show_result=1
+        fi
+    else
+        if [[ "$func_env_value" == "1" || "$func_env_value" == "true" ]]; then
+            show_result=1
+        fi
+    fi
+    if [[ "$show_result" -ne 1 ]]; then
+        return
+    fi
+    cat <<EOF
+$(echo -e "\e[2m")----------------------
+$(cat "$LLM_OUTPUT")
+----------------------$(echo -e "\e[0m")
+EOF
+}
+
+main "$@"