From 6495c64dac54c8e1e527fee72f5488b240f69579 Mon Sep 17 00:00:00 2001
From: Henry Heng <henryheng@flowiseai.com>
Date: Sat, 7 Jun 2025 16:23:42 +0100
Subject: [PATCH] Feat/add headers to custom mcp (#4581)

* add headers to custom mcp

* Refactor MCP fetch method and update CustomMCP documentation to include variable usage in headers
---
 .../nodes/tools/MCP/CustomMCP/CustomMCP.ts    | 10 ++++++++
 packages/components/nodes/tools/MCP/core.ts   | 23 +++++++++++++++++--
 2 files changed, 31 insertions(+), 2 deletions(-)

diff --git a/packages/components/nodes/tools/MCP/CustomMCP/CustomMCP.ts b/packages/components/nodes/tools/MCP/CustomMCP/CustomMCP.ts
index c782a357c..d81c5d778 100644
--- a/packages/components/nodes/tools/MCP/CustomMCP/CustomMCP.ts
+++ b/packages/components/nodes/tools/MCP/CustomMCP/CustomMCP.ts
@@ -27,6 +27,16 @@ For example, you have a variable called "var1":
     }
 }
 \`\`\`
+
+For example, when using SSE, you can use the variable "var1" in the headers:
+\`\`\`json
+{
+    "url": "https://api.example.com/endpoint/sse",
+    "headers": {
+        "Authorization": "Bearer {{$vars.var1}}"
+    }
+}
+\`\`\`
 `
 
 class Custom_MCP implements INode {
diff --git a/packages/components/nodes/tools/MCP/core.ts b/packages/components/nodes/tools/MCP/core.ts
index 7c894fcc4..9ac0ab1ae 100644
--- a/packages/components/nodes/tools/MCP/core.ts
+++ b/packages/components/nodes/tools/MCP/core.ts
@@ -53,10 +53,29 @@ export class MCPToolkit extends BaseToolkit {
 
             const baseUrl = new URL(this.serverParams.url)
             try {
-                transport = new StreamableHTTPClientTransport(baseUrl)
+                if (this.serverParams.headers) {
+                    transport = new StreamableHTTPClientTransport(baseUrl, {
+                        requestInit: {
+                            headers: this.serverParams.headers
+                        }
+                    })
+                } else {
+                    transport = new StreamableHTTPClientTransport(baseUrl)
+                }
                 await client.connect(transport)
             } catch (error) {
-                transport = new SSEClientTransport(baseUrl)
+                if (this.serverParams.headers) {
+                    transport = new SSEClientTransport(baseUrl, {
+                        requestInit: {
+                            headers: this.serverParams.headers
+                        },
+                        eventSourceInit: {
+                            fetch: (url, init) => fetch(url, { ...init, headers: this.serverParams.headers })
+                        }
+                    })
+                } else {
+                    transport = new SSEClientTransport(baseUrl)
+                }
                 await client.connect(transport)
             }
         }