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Registers MCP servers through WithMCPConfig and agent.MCPServers — transport and credentials from env (MCP_*). Contrast with MCP Client, which uses mcpclient.NewClient + WithMCPClients. Source: examples/agent_with_mcp_config/

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What it demonstrates

  • MCPStdio and MCPStreamableHTTP transports from env
  • Tool filters, timeouts, retries per server
  • Local stdio MCP using defaults in .env.defaults — filesystem server pointed at mcp-filesystem-sandbox/ (sample data only, not a separate example)

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Configure MCP

Transport — set MCP_TRANSPORT to stdio or streamable_http. Remote (streamable_http):
  • MCP_STREAMABLE_HTTP_URL — required
  • Auth: MCP_BEARER_TOKEN, or OAuth trio MCP_CLIENT_ID + MCP_CLIENT_SECRET + MCP_TOKEN_URL (OAuth wins when all three set)
  • MCP_SKIP_TLS_VERIFY=true — dev TLS only
Local (stdio):
  • MCP_STDIO_COMMAND and optional MCP_STDIO_ARGS (JSON array), MCP_STDIO_ENV (JSON object)
Shared optional knobs: MCP_SERVER_NAME, MCP_TIMEOUT_SECONDS, MCP_RETRY_ATTEMPTS, MCP_ALLOW_TOOLS / MCP_BLOCK_TOOLS (comma-separated; only one list type). See Configuration and committed .env.defaults in the repo for every variable.

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Run

From examples/: 
go run ./agent_with_mcp_config
go run ./agent_with_mcp_config "List tools you can call."

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Testing against a real HTTP MCP server

This repo does not start an MCP server — point .env at your server. Example with a TypeScript streamable HTTP server on port 8123: 
# In examples/.env:
# MCP_TRANSPORT=streamable_http
# MCP_STREAMABLE_HTTP_URL=http://localhost:8123/mcp
go run ./agent_with_mcp_config
Quick check while the server runs: curl -sS -o /dev/null -w "%{http_code}\n" "http://localhost:8123/mcp" For stdio, set MCP_STDIO_COMMAND (and args/env if needed). The SDK spawns the subprocess and speaks MCP over stdin/stdout.

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Expected output

With the default stdio filesystem MCP server and no prompt: 
I have access to the following MCP tools: read_file, write_file, list_directory,
create_directory, and move_file. These let me interact with the local filesystem
sandbox. How can I help?
The exact tool list reflects what the MCP server advertises on startup. With a remote HTTP server the response depends on that server’s capabilities.

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Learn more

MCP

MCP feature documentation

MCP Client

WithMCPClients variant