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When connecting to MCP servers via streamable HTTP, mcptools was not setting the Accept header. Some servers like mcp.grep.app require clients to accept both application/json and text/event-stream, and return 405 errors when this header is missing. This change ensures the Accept header is always set for both HTTP and SSE transports, fixing compatibility with servers that enforce this requirement. Tested with mcp.grep.app and existing unit tests pass.
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approved these changes
Nov 15, 2025
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Problem
When attempting to connect to certain MCP servers like mcp.grep.app using streamable HTTP transport, mcptools returns a 405 error:
This happens because some MCP servers require the client to include an Accept header that specifies support for both application/json and text/event-stream. Without this header, the server rejects the request.
Solution
This PR modifies the HTTP and SSE transport setup to always include the required Accept header. The change is minimal and affects the header initialization in
cmd/mcptools/commands/utils.go.The fix also simplifies the existing logic by removing conditional header passing, since we now always have at least the Accept header to send.
Testing
Verified the fix works with mcp.grep.app:
$ ./mcp tools https://mcp.grep.app searchGitHub(query:str, [language:str[]], [matchCase:bool], ...) Find real-world code examples from over a million public GitHub repositories...All existing unit tests continue to pass.