feat: headers override for MCP operations

nodes/McpClient/McpClient.node.ts

@@ -12,6 +12,7 @@ import { RequestOptions } from '@modelcontextprotocol/sdk/shared/protocol';
 import { StdioClientTransport } from '@modelcontextprotocol/sdk/client/stdio.js';
 import { Transport } from '@modelcontextprotocol/sdk/shared/transport.js';
 import { CallToolResultSchema } from '@modelcontextprotocol/sdk/types.js';
+import { parseHeaders, mergeHeaders } from './utils';
 
 // Add Node.js process type declaration
 declare const process: {
@@ -100,6 +101,19 @@ export class McpClient implements INodeType {
 				default: '',
 				description: 'Override the URL from credentials with a custom URL',
 			},
+			{
+				displayName: 'Headers Override',
+				name: 'headersOverride',
+				type: 'string',
+				displayOptions: {
+					show: {
+						connectionType: ['sse', 'http'],
+					},
+				},
+				default: '',
+				description:
+					'Additional headers to send in the request in NAME=VALUE format, separated by newlines (e.g., Authorization=Bearer token). These will be merged with headers from credentials, with override headers taking precedence.',
+			},
 			{
 				displayName: 'Operation',
 				name: 'operation',
@@ -248,23 +262,20 @@ export class McpClient implements INodeType {
 				const messagesPostEndpoint = (httpCredentials.messagesPostEndpoint as string) || '';
 				timeout = httpCredentials.httpTimeout as number || 60000;
 
-				// Parse headers
-				let headers: Record<string, string> = {};
-				if (httpCredentials.headers) {
-					const headerLines = (httpCredentials.headers as string).split('\n');
-					for (const line of headerLines) {
-						const equalsIndex = line.indexOf('=');
-						// Ensure '=' is present and not the first character of the line
-						if (equalsIndex > 0) {
-							const name = line.substring(0, equalsIndex).trim();
-							const value = line.substring(equalsIndex + 1).trim();
-							// Add to headers object if key is not empty and value is defined
-							if (name && value !== undefined) {
-								headers[name] = value;
-							}
-						}
-					}
+				// Parse headers from credentials
+				const credentialHeaders = parseHeaders((httpCredentials.headers as string) || '');
+
+				// Get headers override
+				let headersOverrideStr = '';
+				try {
+					headersOverrideStr = this.getNodeParameter('headersOverride', 0, '') as string;
+				} catch (error) {
+					// Parameter doesn't exist, ignore
 				}
+				const overrideHeaders = parseHeaders(headersOverrideStr);
+
+				// Merge headers with override headers taking precedence
+				const headers = mergeHeaders(credentialHeaders, overrideHeaders);
 
 				const requestInit: RequestInit = { headers };
 				if (messagesPostEndpoint) {
@@ -299,23 +310,20 @@ export class McpClient implements INodeType {
 				const messagesPostEndpoint = (sseCredentials.messagesPostEndpoint as string) || '';
 				timeout = sseCredentials.sseTimeout as number || 60000;
 
-				// Parse headers
-				let headers: Record<string, string> = {};
-				if (sseCredentials.headers) {
-					const headerLines = (sseCredentials.headers as string).split('\n');
-					for (const line of headerLines) {
-						const equalsIndex = line.indexOf('=');
-						// Ensure '=' is present and not the first character of the line
-						if (equalsIndex > 0) {
-							const name = line.substring(0, equalsIndex).trim();
-							const value = line.substring(equalsIndex + 1).trim();
-							// Add to headers object if key is not empty and value is defined
-							if (name && value !== undefined) {
-								headers[name] = value;
-							}
-						}
-					}
+				// Parse headers from credentials
+				const credentialHeaders = parseHeaders((sseCredentials.headers as string) || '');
+
+				// Get headers override
+				let headersOverrideStr = '';
+				try {
+					headersOverrideStr = this.getNodeParameter('headersOverride', 0, '') as string;
+				} catch (error) {
+					// Parameter doesn't exist, ignore
 				}
+				const overrideHeaders = parseHeaders(headersOverrideStr);
+
+				// Merge headers with override headers taking precedence
+				const headers = mergeHeaders(credentialHeaders, overrideHeaders);
 
 				// Create SSE transport with dynamic import to avoid TypeScript errors
 				transport = new SSEClientTransport(

nodes/McpClient/__tests__/utils.test.ts

@@ -0,0 +1,137 @@
+import { parseHeaders, mergeHeaders } from '../utils';
+
+describe('MCP Client Utils', () => {
+	describe('parseHeaders', () => {
+		it('should parse newline-separated NAME=VALUE headers', () => {
+			const input = 'Authorization=Bearer token123\nContent-Type=application/json';
+			const result = parseHeaders(input);
+			expect(result).toEqual({
+				Authorization: 'Bearer token123',
+				'Content-Type': 'application/json',
+			});
+		});
+
+		it('should handle headers with equals signs in values', () => {
+			const input = 'Api-Key=abc=def=ghi';
+			const result = parseHeaders(input);
+			expect(result).toEqual({
+				'Api-Key': 'abc=def=ghi',
+			});
+		});
+
+		it('should ignore empty lines and malformed entries', () => {
+			const input = 'Valid-Header=value\n\n=NoKey\nNoEquals\nAnother-Header=value2';
+			const result = parseHeaders(input);
+			expect(result).toEqual({
+				'Valid-Header': 'value',
+				'Another-Header': 'value2',
+			});
+		});
+
+		it('should trim whitespace from keys and values', () => {
+			const input = '  Authorization  =  Bearer token  \n  Content-Type  =  application/json  ';
+			const result = parseHeaders(input);
+			expect(result).toEqual({
+				Authorization: 'Bearer token',
+				'Content-Type': 'application/json',
+			});
+		});
+
+		it('should handle empty string input', () => {
+			const result = parseHeaders('');
+			expect(result).toEqual({});
+		});
+
+		it('should handle multiple headers with various formats', () => {
+			const input =
+				'X-Api-Key=secret123\nAuthorization=Bearer xyz\nX-Custom-Header=value=with=equals';
+			const result = parseHeaders(input);
+			expect(result).toEqual({
+				'X-Api-Key': 'secret123',
+				Authorization: 'Bearer xyz',
+				'X-Custom-Header': 'value=with=equals',
+			});
+		});
+	});
+
+	describe('mergeHeaders', () => {
+		it('should merge credential and override headers', () => {
+			const credentialHeaders = {
+				'X-Api-Key': 'from-credentials',
+				'Content-Type': 'application/json',
+			};
+			const overrideHeaders = {
+				Authorization: 'Bearer override-token',
+			};
+			const result = mergeHeaders(credentialHeaders, overrideHeaders);
+			expect(result).toEqual({
+				'X-Api-Key': 'from-credentials',
+				'Content-Type': 'application/json',
+				Authorization: 'Bearer override-token',
+			});
+		});
+
+		it('should allow override headers to take precedence over credential headers', () => {
+			const credentialHeaders = {
+				Authorization: 'Bearer credential-token',
+				'X-Custom': 'credential-value',
+			};
+			const overrideHeaders = {
+				Authorization: 'Bearer override-token',
+			};
+			const result = mergeHeaders(credentialHeaders, overrideHeaders);
+			expect(result).toEqual({
+				Authorization: 'Bearer override-token',
+				'X-Custom': 'credential-value',
+			});
+		});
+
+		it('should handle empty override headers', () => {
+			const credentialHeaders = {
+				Authorization: 'Bearer token',
+			};
+			const overrideHeaders = {};
+			const result = mergeHeaders(credentialHeaders, overrideHeaders);
+			expect(result).toEqual({
+				Authorization: 'Bearer token',
+			});
+		});
+
+		it('should handle empty credential headers', () => {
+			const credentialHeaders = {};
+			const overrideHeaders = {
+				Authorization: 'Bearer token',
+			};
+			const result = mergeHeaders(credentialHeaders, overrideHeaders);
+			expect(result).toEqual({
+				Authorization: 'Bearer token',
+			});
+		});
+
+		it('should handle both empty headers objects', () => {
+			const credentialHeaders = {};
+			const overrideHeaders = {};
+			const result = mergeHeaders(credentialHeaders, overrideHeaders);
+			expect(result).toEqual({});
+		});
+
+		it('should merge multiple headers correctly', () => {
+			const credentialHeaders = {
+				'X-Api-Key': 'cred-key',
+				'Content-Type': 'application/json',
+				Accept: 'application/json',
+			};
+			const overrideHeaders = {
+				Authorization: 'Bearer new-token',
+				'Content-Type': 'text/plain',
+			};
+			const result = mergeHeaders(credentialHeaders, overrideHeaders);
+			expect(result).toEqual({
+				'X-Api-Key': 'cred-key',
+				'Content-Type': 'text/plain',
+				Accept: 'application/json',
+				Authorization: 'Bearer new-token',
+			});
+		});
+	});
+});

nodes/McpClient/utils.ts

@@ -0,0 +1,33 @@
+/**
+ * Parse headers from newline-separated NAME=VALUE format
+ */
+export function parseHeaders(headerString: string): Record<string, string> {
+	const headers: Record<string, string> = {};
+	if (headerString) {
+		const headerLines = headerString.split('\n');
+		for (const line of headerLines) {
+			const equalsIndex = line.indexOf('=');
+			// Ensure '=' is present and not the first character of the line
+			if (equalsIndex > 0) {
+				const name = line.substring(0, equalsIndex).trim();
+				const value = line.substring(equalsIndex + 1).trim();
+				// Add to headers object if key is not empty and value is defined
+				if (name && value !== undefined) {
+					headers[name] = value;
+				}
+			}
+		}
+	}
+	return headers;
+}
+
+/**
+ * Merge headers from credentials with dynamic headers
+ * Dynamic headers take precedence over credential headers
+ */
+export function mergeHeaders(
+	credentialHeaders: Record<string, string>,
+	dynamicHeaders: Record<string, string>,
+): Record<string, string> {
+	return { ...credentialHeaders, ...dynamicHeaders };
+}