diff --git a/erpnext-mcp/src/services/erpnext-client.ts b/erpnext-mcp/src/services/erpnext-client.ts
new file mode 100644
index 0000000..3b68ac5
--- /dev/null
+++ b/erpnext-mcp/src/services/erpnext-client.ts
@@ -0,0 +1,434 @@
+import { ERPNextConfig, ERPNextListParams, PaginatedResult } from "../types.js";
+import { RESOURCE_PATH, METHOD_PATH, CHARACTER_LIMIT, DEFAULT_PAGE_SIZE } from "../constants.js";
+
+export class ERPNextClient {
+  private baseUrl: string;
+  private authHeader: string;
+
+  constructor(config: ERPNextConfig) {
+    this.baseUrl = config.baseUrl.replace(/\/$/, "");
+    this.authHeader = `token ${config.apiKey}:${config.apiSecret}`;
+  }
+
+  private async request<T>(
+    path: string,
+    method: string = "GET",
+    body?: Record<string, unknown>,
+    params?: Record<string, string>
+  ): Promise<T> {
+    let url = `${this.baseUrl}${path}`;
+    if (params) {
+      const searchParams = new URLSearchParams();
+      for (const [key, value] of Object.entries(params)) {
+        if (value !== undefined && value !== null && value !== "") {
+          searchParams.append(key, value);
+        }
+      }
+      const qs = searchParams.toString();
+      if (qs) url += `?${qs}`;
+    }
+
+    const headers: Record<string, string> = {
+      Authorization: this.authHeader,
+      "Content-Type": "application/json",
+      Accept: "application/json",
+    };
+
+    const fetchOptions: RequestInit = { method, headers };
+    if (body && (method === "POST" || method === "PUT" || method === "DELETE")) {
+      fetchOptions.body = JSON.stringify(body);
+    }
+
+    const response = await fetch(url, fetchOptions);
+
+    if (!response.ok) {
+      const errorText = await response.text();
+      let errorMessage: string;
+      try {
+        const errorJson = JSON.parse(errorText);
+        errorMessage =
+          errorJson.message ||
+          errorJson.exc ||
+          errorJson._server_messages ||
+          errorText;
+        if (typeof errorMessage !== "string") {
+          errorMessage = JSON.stringify(errorMessage);
+        }
+      } catch {
+        errorMessage = errorText;
+      }
+      throw new Error(
+        `ERPNext API error (${response.status} ${response.statusText}): ${errorMessage.slice(0, 500)}`
+      );
+    }
+
+    const json = await response.json();
+    return json as T;
+  }
+
+  // ── Generic CRUD ──────────────────────────────────────────
+
+  async listDocuments(
+    doctype: string,
+    listParams?: ERPNextListParams
+  ): Promise<PaginatedResult<Record<string, unknown>>> {
+    const params: Record<string, string> = {};
+
+    if (listParams?.fields?.length) {
+      params.fields = JSON.stringify(listParams.fields);
+    }
+    if (listParams?.filters?.length) {
+      params.filters = JSON.stringify(listParams.filters);
+    }
+    if (listParams?.or_filters?.length) {
+      params.or_filters = JSON.stringify(listParams.or_filters);
+    }
+    if (listParams?.order_by) {
+      params.order_by = listParams.order_by;
+    }
+    if (listParams?.group_by) {
+      params.group_by = listParams.group_by;
+    }
+
+    const offset = listParams?.limit_start ?? 0;
+    const limit = listParams?.limit_page_length ?? DEFAULT_PAGE_SIZE;
+    params.limit_start = String(offset);
+    params.limit_page_length = String(limit);
+
+    const result = await this.request<{ data: Record<string, unknown>[] }>(
+      `${RESOURCE_PATH}/${encodeURIComponent(doctype)}`,
+      "GET",
+      undefined,
+      params
+    );
+
+    // Get total count
+    const countParams: Record<string, string> = {};
+    if (listParams?.filters?.length) {
+      countParams.filters = JSON.stringify(listParams.filters);
+    }
+    if (listParams?.or_filters?.length) {
+      countParams.or_filters = JSON.stringify(listParams.or_filters);
+    }
+    countParams.limit_page_length = "0";
+
+    let total = result.data.length + offset;
+    try {
+      const countResult = await this.request<{ data: number }>(
+        `${METHOD_PATH}/frappe.client.get_count`,
+        "GET",
+        undefined,
+        {
+          doctype,
+          ...(listParams?.filters?.length
+            ? { filters: JSON.stringify(listParams.filters) }
+            : {}),
+        }
+      );
+      total = countResult.data ?? (countResult as unknown as { message: number }).message ?? total;
+    } catch {
+      // If count fails, estimate based on returned data
+      if (result.data.length === limit) {
+        total = offset + limit + 1; // Signal there might be more
+      }
+    }
+
+    return {
+      total,
+      count: result.data.length,
+      offset,
+      items: result.data,
+      has_more: offset + result.data.length < total,
+      ...(offset + result.data.length < total
+        ? { next_offset: offset + result.data.length }
+        : {}),
+    };
+  }
+
+  async getDocument(
+    doctype: string,
+    name: string,
+    fields?: string[]
+  ): Promise<Record<string, unknown>> {
+    const params: Record<string, string> = {};
+    if (fields?.length) {
+      params.fields = JSON.stringify(fields);
+    }
+    const result = await this.request<{ data: Record<string, unknown> }>(
+      `${RESOURCE_PATH}/${encodeURIComponent(doctype)}/${encodeURIComponent(name)}`,
+      "GET",
+      undefined,
+      params
+    );
+    return result.data;
+  }
+
+  async createDocument(
+    doctype: string,
+    data: Record<string, unknown>
+  ): Promise<Record<string, unknown>> {
+    const result = await this.request<{ data: Record<string, unknown> }>(
+      `${RESOURCE_PATH}/${encodeURIComponent(doctype)}`,
+      "POST",
+      data
+    );
+    return result.data;
+  }
+
+  async updateDocument(
+    doctype: string,
+    name: string,
+    data: Record<string, unknown>
+  ): Promise<Record<string, unknown>> {
+    const result = await this.request<{ data: Record<string, unknown> }>(
+      `${RESOURCE_PATH}/${encodeURIComponent(doctype)}/${encodeURIComponent(name)}`,
+      "PUT",
+      data
+    );
+    return result.data;
+  }
+
+  async deleteDocument(
+    doctype: string,
+    name: string
+  ): Promise<{ message: string }> {
+    const result = await this.request<{ message: string }>(
+      `${RESOURCE_PATH}/${encodeURIComponent(doctype)}/${encodeURIComponent(name)}`,
+      "DELETE"
+    );
+    return result;
+  }
+
+  // ── Workflow / Submit / Cancel / Amend ────────────────────
+
+  async submitDocument(
+    doctype: string,
+    name: string
+  ): Promise<Record<string, unknown>> {
+    return this.updateDocument(doctype, name, { docstatus: 1 });
+  }
+
+  async cancelDocument(
+    doctype: string,
+    name: string
+  ): Promise<Record<string, unknown>> {
+    return this.updateDocument(doctype, name, { docstatus: 2 });
+  }
+
+  async amendDocument(
+    doctype: string,
+    name: string
+  ): Promise<Record<string, unknown>> {
+    const result = await this.callMethod("frappe.client.amend", {
+      doctype,
+      name,
+    });
+    return result as Record<string, unknown>;
+  }
+
+  // ── Method Calls ──────────────────────────────────────────
+
+  async callMethod(
+    method: string,
+    args?: Record<string, unknown>
+  ): Promise<unknown> {
+    const result = await this.request<{ message: unknown }>(
+      `${METHOD_PATH}/${method}`,
+      "POST",
+      args
+    );
+    return result.message ?? result;
+  }
+
+  async callGetMethod(
+    method: string,
+    params?: Record<string, string>
+  ): Promise<unknown> {
+    const result = await this.request<{ message: unknown }>(
+      `${METHOD_PATH}/${method}`,
+      "GET",
+      undefined,
+      params
+    );
+    return result.message ?? result;
+  }
+
+  // ── Search / Link ─────────────────────────────────────────
+
+  async searchLink(
+    doctype: string,
+    txt: string,
+    filters?: Record<string, unknown>,
+    pageLength?: number
+  ): Promise<Array<{ value: string; description: string }>> {
+    const params: Record<string, string> = {
+      doctype,
+      txt,
+      page_length: String(pageLength ?? 20),
+    };
+    if (filters) {
+      params.filters = JSON.stringify(filters);
+    }
+    const result = await this.callGetMethod(
+      "frappe.desk.search.search_link",
+      params
+    );
+    return result as Array<{ value: string; description: string }>;
+  }
+
+  // ── Report ────────────────────────────────────────────────
+
+  async runReport(
+    reportName: string,
+    filters?: Record<string, unknown>
+  ): Promise<unknown> {
+    return this.callMethod("frappe.desk.query_report.run", {
+      report_name: reportName,
+      filters: filters ?? {},
+    });
+  }
+
+  // ── File upload ───────────────────────────────────────────
+
+  async getFileUrl(fileName: string): Promise<string> {
+    return `${this.baseUrl}/api/method/frappe.client.get_file?file_name=${encodeURIComponent(fileName)}`;
+  }
+
+  // ── Print format ──────────────────────────────────────────
+
+  async getPrintFormat(
+    doctype: string,
+    name: string,
+    printFormat?: string
+  ): Promise<string> {
+    const params: Record<string, string> = {
+      doctype,
+      name,
+      format: printFormat ?? "Standard",
+    };
+    const result = await this.callGetMethod(
+      "frappe.utils.print_format.download_pdf",
+      params
+    );
+    return result as string;
+  }
+
+  // ── Get count ─────────────────────────────────────────────
+
+  async getCount(
+    doctype: string,
+    filters?: Array<[string, string, string, string | number | boolean]>
+  ): Promise<number> {
+    const params: Record<string, string> = { doctype };
+    if (filters?.length) {
+      params.filters = JSON.stringify(filters);
+    }
+    const result = await this.callGetMethod("frappe.client.get_count", params);
+    return result as number;
+  }
+
+  // ── Get list of DocTypes ──────────────────────────────────
+
+  async getDocTypeList(): Promise<string[]> {
+    const result = await this.listDocuments("DocType", {
+      fields: ["name"],
+      limit_page_length: 500,
+      order_by: "name asc",
+    });
+    return result.items.map((d) => d.name as string);
+  }
+
+  // ── Get DocType schema/meta ───────────────────────────────
+
+  async getDocTypeMeta(
+    doctype: string
+  ): Promise<Record<string, unknown>> {
+    const result = await this.callGetMethod("frappe.client.get_list", {
+      doctype: "DocField",
+      filters: JSON.stringify([["parent", "=", doctype]]),
+      fields: JSON.stringify([
+        "fieldname",
+        "fieldtype",
+        "label",
+        "options",
+        "reqd",
+        "read_only",
+        "hidden",
+      ]),
+      limit_page_length: "500",
+      order_by: "idx asc",
+    });
+    return { doctype, fields: result };
+  }
+}
+
+// ── Response Formatting Helpers ───────────────────────────
+
+export function truncateResponse(text: string): string {
+  if (text.length <= CHARACTER_LIMIT) return text;
+  return (
+    text.slice(0, CHARACTER_LIMIT) +
+    `\n\n--- Response truncated (${text.length} chars). Use filters, pagination, or narrower field selection to get more targeted results. ---`
+  );
+}
+
+export function formatDocumentMarkdown(
+  doc: Record<string, unknown>,
+  doctype?: string
+): string {
+  const lines: string[] = [];
+  if (doctype) {
+    lines.push(`# ${doctype}: ${doc.name ?? "Unknown"}`);
+  } else {
+    lines.push(`# ${doc.name ?? "Document"}`);
+  }
+  lines.push("");
+
+  for (const [key, value] of Object.entries(doc)) {
+    if (
+      value === null ||
+      value === undefined ||
+      value === "" ||
+      key.startsWith("_")
+    )
+      continue;
+    if (Array.isArray(value)) {
+      lines.push(`**${key}**: [${value.length} items]`);
+    } else if (typeof value === "object") {
+      lines.push(`**${key}**: ${JSON.stringify(value)}`);
+    } else {
+      lines.push(`**${key}**: ${value}`);
+    }
+  }
+  return lines.join("\n");
+}
+
+export function formatListMarkdown(
+  items: Record<string, unknown>[],
+  doctype: string,
+  pagination: { total: number; offset: number; has_more: boolean }
+): string {
+  const lines: string[] = [
+    `# ${doctype} List`,
+    `Showing ${items.length} of ${pagination.total} (offset: ${pagination.offset})`,
+    "",
+  ];
+
+  for (const item of items) {
+    const name = item.name ?? "unnamed";
+    const summary = Object.entries(item)
+      .filter(([k]) => k !== "name")
+      .map(([k, v]) => `${k}: ${v}`)
+      .join(" | ");
+    lines.push(`- **${name}**${summary ? ` — ${summary}` : ""}`);
+  }
+
+  if (pagination.has_more) {
+    lines.push(
+      "",
+      `_More results available. Use offset=${pagination.offset + items.length} to see next page._`
+    );
+  }
+
+  return lines.join("\n");
+}