OpenAI Codex

Connect from OpenAI Codex

Codex CLI supports remote MCP servers with custom headers natively via a TOML config file.

Configuration File

Edit or create the Codex config:

• User-global: ~/.codex/config.toml
• Project-scoped: .codex/config.toml (in project root)

Using an Environment Variable (Recommended)

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[mcp_servers.atomicwork]
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url = "https://<your-subdomain>.atomicwork.com/api/mcp/sse"
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env_http_headers = { "X-Api-Key" = "ATOMICWORK_API_KEY" }

Then set the environment variable:

$
export ATOMICWORK_API_KEY="your-api-key-here"

Using a Static Key

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[mcp_servers.atomicwork]
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url = "https://<your-subdomain>.atomicwork.com/api/mcp/sse"
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http_headers = { "X-Api-Key" = "<your-api-key>" }

Verify Connection

$
codex mcp

Notes

• Project-scoped config requires the project to be trusted by Codex.
• You can set default_tools_approval_mode = "auto" to skip per-tool confirmation prompts.