# Configure Codex for Tellagen Diagnosis

Add the Tellagen MCP server to Codex and check its tools from Tellagen.

## Before you start

### Intended audience

Responders who use Codex CLI for local incident investigations.

### Required permissions

You need a Tellagen API key with the Local Diagnosis preset. The API key owner needs an active responder seat.


### Prerequisites

- Install Codex CLI.
- Create and store a [Tellagen Local Diagnosis API key](https://tellagen.com/help/manage-api-keys#step-create-and-store-the-token).

## Procedure

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### Configure the client

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1. **Select Codex.** Open Settings. The Settings navigation label is Local investigation tools. The page heading is AI diagnostics. Select Codex.

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2. **Copy the install command.** Find the Tellagen MCP card. Select Copy.

![Local investigation tools page with Codex selected and the Tellagen MCP install command.](https://tellagen.com/help/assets/codex-mcp-setup-command-2026-08-29.webp)

Use the command shown for Codex, then check the installed tools.

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3. **Add the MCP server.** Run codex mcp add with the copied environment values and stdio command. Codex stores the server configuration.

Codex command with safe placeholders:

```shell
codex mcp add tellagen \
  --env TELLAGEN_API_KEY=tllg_YOUR_TOKEN \
  --env TELLAGEN_API_URL=https://YOUR_WORKSPACE.api.tellagen.com \
  --env TELLAGEN_MCP_CLIENT=codex \
  -- npx -y @tellagen/mcp-server@latest
```

<a id="step-add-required-provider-tools"></a>

4. **Add required provider tools.** Install only the provider tools that the incident needs. Keep provider credentials in Codex.

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### Verify access

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5. **Review the Codex server list.** Run codex mcp list. Make sure that the Tellagen server appears.

Local configuration check:

```shell
codex mcp list
```

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6. **Check the tools.** In Tellagen, select Check MCP tools. Paste the prompt into Codex.

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7. **Review the result.** Return to Tellagen. Make sure that required tool cards show INSTALLED and ACCESS OK.

## You are done when…

Codex can discover the Tellagen MCP server and its allowed incident tools.

## Troubleshooting

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### Codex shows Auth: Unsupported.

This local connection uses TELLAGEN_API_KEY in the MCP configuration; the status does not mean the Tellagen key is invalid.

<a id="troubleshooting-no-diagnostic-tools-are-available"></a>

### No diagnostic tools are available.

Confirm the Codex command was installed and the required local tools are enabled, then run [Check MCP tools again](https://tellagen.com/help/run-local-diagnosis#step-check-local-setup).

<a id="troubleshooting-codex-mcp-list-does-not-show-tellagen"></a>

### codex mcp list does not show Tellagen.

Run the copied codex mcp add command again. Existing incident work stays in Tellagen. If the server still does not appear, ask the local client administrator to inspect the Codex configuration.

<a id="troubleshooting-tellagen-shows-access-denied"></a>

### Tellagen shows ACCESS denied.

Replace the local token with a Local Diagnosis key. Do not remove the saved investigation. If access still fails, ask a workspace manager to review the key scopes.

## Related articles

- **Recommended next task:** [Run a local Diagnosis for an incident](https://tellagen.com/help/run-local-diagnosis)
- [Configure MCP tools for Diagnosis](https://tellagen.com/help/configure-mcp-tools-for-diagnosis)
- [Manage API keys](https://tellagen.com/help/manage-api-keys)

## External setup references

- [OpenAI Codex MCP documentation](https://learn.chatgpt.com/docs/extend/mcp?surface=cli) (verified 2026-08-29)


## Continue through the incident lifecycle

- **Previous task:** [Manage workspace API keys](https://tellagen.com/help/manage-api-keys)
- **Next task:** [Configure Claude for Tellagen Diagnosis](https://tellagen.com/help/configure-claude-for-diagnosis)
- [Back to Support Center](https://tellagen.com/help#help-search)

## Last verified date

2026-08-29