feat: support custom HTTP headers from tool parameters in OneMcpServer - #10902
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This pull request adds support for forwarding custom HTTP headers (Mcp-Param-*) to remote MCP tools when defined in tool parameter input schemas (x-mcp-header), per SEP-2243. It updates OneMcpServer to parse the tool's inputSchema and extract parameters mapped to headers, forwarding them during tool execution, and includes corresponding unit tests. The feedback suggests reducing nesting in the parameter-extraction loop by using continue statements to align with the repository's style guide.
joehan
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Aug 7, 2026
### Description Adds support for forwarding custom HTTP headers (Mcp-Param-*) to remote MCP tools when defined in tool input parameter schemas via the x-mcp-header property per [SEP-2243](https://modelcontextprotocol.io/seps/2243-http-standardization). When OneMcpServer executes a tools/call request to a remote MCP backend, it inspects tool.inputSchema.properties for "x-mcp-header": "HeaderName". If present and the corresponding argument is supplied in args, OneMcpServer attaches Mcp-Param-<HeaderName>: <value> to the outbound HTTP request headers. Bug: 530219396 ### Scenarios Tested 1. Tested listTools() and verified tool schema mapping remains unchanged. 2. Tested callTool() with a tool having "x-mcp-header": "Region" in inputSchema.properties and verified Mcp-Param-Region: us-west1 is included in outbound POST headers to remote MCP servers. 3. Tested callTool() without x-mcp-header properties to ensure no extra headers are injected. 4. Ran unit tests (npx mocha src/mcp/onemcp/onemcp_server.spec.ts) and linters (npm run lint:changed-files). ### Sample Commands - npx mocha src/mcp/onemcp/onemcp_server.spec.ts
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firebase#10902) ### Description Adds support for forwarding custom HTTP headers (Mcp-Param-*) to remote MCP tools when defined in tool input parameter schemas via the x-mcp-header property per [SEP-2243](https://modelcontextprotocol.io/seps/2243-http-standardization). When OneMcpServer executes a tools/call request to a remote MCP backend, it inspects tool.inputSchema.properties for "x-mcp-header": "HeaderName". If present and the corresponding argument is supplied in args, OneMcpServer attaches Mcp-Param-<HeaderName>: <value> to the outbound HTTP request headers. Bug: 530219396 ### Scenarios Tested 1. Tested listTools() and verified tool schema mapping remains unchanged. 2. Tested callTool() with a tool having "x-mcp-header": "Region" in inputSchema.properties and verified Mcp-Param-Region: us-west1 is included in outbound POST headers to remote MCP servers. 3. Tested callTool() without x-mcp-header properties to ensure no extra headers are injected. 4. Ran unit tests (npx mocha src/mcp/onemcp/onemcp_server.spec.ts) and linters (npm run lint:changed-files). ### Sample Commands - npx mocha src/mcp/onemcp/onemcp_server.spec.ts
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Description
Adds support for forwarding custom HTTP headers (
Mcp-Param-*) to remote MCP tools when defined in tool input parameter schemas via thex-mcp-headerproperty per SEP-2243.When OneMcpServer executes a
tools/callrequest to a remote MCP backend, it inspectstool.inputSchema.propertiesfor"x-mcp-header": "HeaderName". If present and the corresponding argument is supplied in args, OneMcpServer attachesMcp-Param-<HeaderName>: <value>to the outbound HTTP request headers.Bug: 530219396
Scenarios Tested
Sample Commands