LINE Bot MCP Server

Instructions

Implementation Reference

• src/tools/pushGeminiText.ts:53-153 (handler)

  The core handler function for the 'push_gemini_text' tool. It checks for userId and API key, calls the Gemini API with fallback logic for models ('gemini-1.5-flash' etc.) and API versions (v1/v1beta), extracts the generated text, truncates to 2000 characters (LINE limit), and pushes it as a text message to the specified LINE user using the messaging client.
  async ({ userId, prompt, model }) => { if (!userId) { return createErrorResponse(NO_USER_ID_ERROR); } const apiKey = process.env.GEMINI_API_KEY || process.env.GOOGLE_API_KEY; if (!apiKey) { return createErrorResponse( "Please set GEMINI_API_KEY (or GOOGLE_API_KEY) in environment variables.", ); } try { async function callGeminiOnce( modelName: string, apiVersion: "v1" | "v1beta", ) { const endpoint = `https://generativelanguage.googleapis.com/${apiVersion}/models/${encodeURIComponent( modelName, )}:generateContent`; const body = { contents: [ { role: "user", parts: [{ text: prompt }], }, ], }; const res = await fetch(endpoint, { method: "POST", headers: { "Content-Type": "application/json", "X-goog-api-key": apiKey, }, body: JSON.stringify(body), }); return res; } const tryModels: string[] = [model]; if (!model.endsWith("-latest")) tryModels.push(`${model}-latest`); for (const m of [ "gemini-2.0-flash", "gemini-2.0-flash-latest", "gemini-1.5-flash-latest", ]) { if (!tryModels.includes(m)) tryModels.push(m); } let res: Response | undefined; let lastErrorText = ""; for (const m of tryModels) { for (const ver of ["v1", "v1beta"] as const) { res = await callGeminiOnce(m, ver); if (res.ok) { break; } lastErrorText = await res.text(); if (res.status !== 404) break; } if (res?.ok) break; } if (!res || !res.ok) { return createErrorResponse( `Gemini API error: HTTP ${res?.status} ${res?.statusText} - ${lastErrorText}`, ); } const data = (await res.json()) as GenerateContentResponse; const generated = data?.candidates?.[0]?.content?.parts ?.map(p => p.text || "") .join("") || ""; if (!generated) { return createErrorResponse( data?.error?.message || "Gemini returned empty content.", ); } // LINE text message limit is 2000 chars const textMessage = generated.slice(0, 2000); const response = await this.client.pushMessage({ to: userId, messages: [ { type: "text", text: textMessage, } as unknown as messagingApi.Message, ], }); return createSuccessResponse(response); } catch (error: any) { return createErrorResponse( `Failed to push Gemini text: ${error.message}`, ); } },
• src/tools/pushGeminiText.ts:31-52 (schema)

  Zod input schemas for the tool parameters: userId (string, default destinationId), model (string, default 'gemini-1.5-flash'), prompt (non-empty string). Used in server.tool call.
  const userIdSchema = z .string() .default(this.destinationId) .describe( "The user ID to receive a message. Defaults to DESTINATION_USER_ID.", ); const modelSchema = z .string() .default("gemini-1.5-flash") .describe("Gemini model name, e.g., gemini-1.5-flash"); const promptSchema = z.string().min(1).describe("Prompt to send to Gemini"); server.tool( "push_gemini_text", "Generate text with Gemini and push it to a LINE user as a text message.", { userId: userIdSchema, prompt: promptSchema, model: modelSchema, },
• src/index.ts:24-71 (registration)

  Imports the PushGeminiText class and instantiates it with the LINE messaging client and destination ID, then calls .register(server) to register all tools including 'push_gemini_text' with the MCP server.
  import PushGeminiText from "./tools/pushGeminiText.js"; import CancelRichMenuDefault from "./tools/cancelRichMenuDefault.js"; import PushTextMessage from "./tools/pushTextMessage.js"; import PushFlexMessage from "./tools/pushFlexMessage.js"; import BroadcastTextMessage from "./tools/broadcastTextMessage.js"; import BroadcastFlexMessage from "./tools/broadcastFlexMessage.js"; import GetProfile from "./tools/getProfile.js"; import GetMessageQuota from "./tools/getMessageQuota.js"; import GetRichMenuList from "./tools/getRichMenuList.js"; import DeleteRichMenu from "./tools/deleteRichMenu.js"; import SetRichMenuDefault from "./tools/setRichMenuDefault.js"; import PushGeminiFlex from "./tools/pushGeminiFlex.js"; import GeminiCommand from "./tools/geminiCommand.js"; import PushMessages from "./tools/pushMessages.js"; import BroadcastMessages from "./tools/broadcastMessages.js"; import QueryMssql from "./tools/queryMssql.js"; import ExportMssqlKnowledge from "./tools/exportMssqlKnowledge.js"; import AiQueryMssql from "./tools/aiQueryMssql.js"; // Load environment variables from .env if present (no external deps) loadEnvFromDotenv(); const server = new McpServer({ name: "line-bot", version: LINE_BOT_MCP_SERVER_VERSION, }); const channelAccessToken = process.env.CHANNEL_ACCESS_TOKEN || ""; const destinationId = process.env.DESTINATION_USER_ID || ""; const messagingApiClient = new line.messagingApi.MessagingApiClient({ channelAccessToken: channelAccessToken, defaultHeaders: { "User-Agent": USER_AGENT, }, }); new PushTextMessage(messagingApiClient, destinationId).register(server); new PushFlexMessage(messagingApiClient, destinationId).register(server); new BroadcastTextMessage(messagingApiClient).register(server); new BroadcastFlexMessage(messagingApiClient).register(server); new GetProfile(messagingApiClient, destinationId).register(server); new GetMessageQuota(messagingApiClient).register(server); new GetRichMenuList(messagingApiClient).register(server); new DeleteRichMenu(messagingApiClient).register(server); new SetRichMenuDefault(messagingApiClient).register(server); new CancelRichMenuDefault(messagingApiClient).register(server); new PushGeminiText(messagingApiClient, destinationId).register(server);
• src/tools/pushGeminiText.ts:45-154 (registration)

  Inside the PushGeminiText class's register method, calls server.tool to register the 'push_gemini_text' tool with its name, description, input schema, and handler function.
  server.tool( "push_gemini_text", "Generate text with Gemini and push it to a LINE user as a text message.", { userId: userIdSchema, prompt: promptSchema, model: modelSchema, }, async ({ userId, prompt, model }) => { if (!userId) { return createErrorResponse(NO_USER_ID_ERROR); } const apiKey = process.env.GEMINI_API_KEY || process.env.GOOGLE_API_KEY; if (!apiKey) { return createErrorResponse( "Please set GEMINI_API_KEY (or GOOGLE_API_KEY) in environment variables.", ); } try { async function callGeminiOnce( modelName: string, apiVersion: "v1" | "v1beta", ) { const endpoint = `https://generativelanguage.googleapis.com/${apiVersion}/models/${encodeURIComponent( modelName, )}:generateContent`; const body = { contents: [ { role: "user", parts: [{ text: prompt }], }, ], }; const res = await fetch(endpoint, { method: "POST", headers: { "Content-Type": "application/json", "X-goog-api-key": apiKey, }, body: JSON.stringify(body), }); return res; } const tryModels: string[] = [model]; if (!model.endsWith("-latest")) tryModels.push(`${model}-latest`); for (const m of [ "gemini-2.0-flash", "gemini-2.0-flash-latest", "gemini-1.5-flash-latest", ]) { if (!tryModels.includes(m)) tryModels.push(m); } let res: Response | undefined; let lastErrorText = ""; for (const m of tryModels) { for (const ver of ["v1", "v1beta"] as const) { res = await callGeminiOnce(m, ver); if (res.ok) { break; } lastErrorText = await res.text(); if (res.status !== 404) break; } if (res?.ok) break; } if (!res || !res.ok) { return createErrorResponse( `Gemini API error: HTTP ${res?.status} ${res?.statusText} - ${lastErrorText}`, ); } const data = (await res.json()) as GenerateContentResponse; const generated = data?.candidates?.[0]?.content?.parts ?.map(p => p.text || "") .join("") || ""; if (!generated) { return createErrorResponse( data?.error?.message || "Gemini returned empty content.", ); } // LINE text message limit is 2000 chars const textMessage = generated.slice(0, 2000); const response = await this.client.pushMessage({ to: userId, messages: [ { type: "text", text: textMessage, } as unknown as messagingApi.Message, ], }); return createSuccessResponse(response); } catch (error: any) { return createErrorResponse( `Failed to push Gemini text: ${error.message}`, ); } }, );