Connect to the AX MCP Server

The MCP server is hosted, so there is nothing to install. You need two things: the endpoint for your region and an Arize API key.

Add the server to your client

Claude Code
Cursor
Codex
Other clients

Registering at project scope writes to .mcp.json in the repository root:

claude mcp add-json arize-ax --scope project '{
  "type": "http",
  "url": "https://api.arize.com/mcp",
  "headers": {"Authorization": "Bearer ${ARIZE_API_KEY}"}
}'

Use --scope user instead to make the server available in every project on your machine.

Check the connection

Run claude mcp list, which shows whether each server connected, or run /mcp inside Claude Code for interactive status.

Remove it (optional)

Run claude mcp remove arize-ax.

Add the server

Go to Settings → MCP → Add new global MCP server, then add this entry to the JSON config:

"arize-ax": {
  "type": "http",
  "url": "https://api.arize.com/mcp",
  "headers": {"Authorization": "Bearer ${ARIZE_API_KEY}"}
}

Restart Cursor

Restart Cursor if the tools do not appear.

Registering with the CLI writes to ~/.codex/config.toml:

codex mcp add arize-ax --url https://api.arize.com/mcp --bearer-token-env-var ARIZE_API_KEY

--bearer-token-env-var points Codex at the name of the environment variable holding your key, so the key itself never lands in config.toml. Codex sends it as Authorization: Bearer <value> on every request.

Check the connection

Run codex mcp get arize-ax, or list every configured server with codex mcp list. Remove it with codex mcp remove arize-ax.

Or edit config.toml directly

[mcp_servers.arize-ax]
url = "https://api.arize.com/mcp"
bearer_token_env_var = "ARIZE_API_KEY"

Any client that speaks Streamable HTTP and supports custom headers works. The config shape is the same:

{
  "mcpServers": {
    "arize-ax": {
      "type": "http",
      "url": "https://api.arize.com/mcp",
      "headers": {"Authorization": "Bearer ${ARIZE_API_KEY}"}
    }
  }
}

Some clients expand ${...} from your environment and some do not. If the connection fails with an auth error, replace the placeholder with the key directly to rule it out.A few clients take a top-level "auth" field instead of headers and send it as Authorization: Bearer <key> for you.

Verify the connection

Ask your agent something that requires a tool call, such as “list my Arize projects.” It should call list_projects and come back with names rather than a guess. To test outside a client, use the MCP Inspector CLI. It needs Node 22.19.0 or newer and runs through npx with no install:

npx @modelcontextprotocol/inspector --cli https://api.arize.com/mcp \
  --transport http \
  --header "Authorization: Bearer $ARIZE_API_KEY" \
  --method tools/list \
  --format json | jq .result

Call a tool the same way:

npx @modelcontextprotocol/inspector --cli https://api.arize.com/mcp \
  --transport http \
  --header "Authorization: Bearer $ARIZE_API_KEY" \
  --method tools/call \
  --tool-name list_projects \
  --tool-arg name=my-project \
  --format json | jq .result

The CLI exits non-zero on failure. Exit code 3 means authentication failed and exit code 4 means the server was unreachable.

Troubleshooting

The client connects but no tools appear

Confirm the transport is Streamable HTTP. A client configured for stdio will try to run the URL as a command, and one configured for sse will hang on a connection the server does not offer. Set "type": "http", or pass --transport http on the Inspector CLI.

Authorization errors on every call

The header must be Authorization: Bearer <your-arize-api-key>. The bare key also works, but the word Bearer with nothing after it is rejected.If the value looks right, your client probably did not expand ${ARIZE_API_KEY}. Paste the key directly to confirm, then move it back into an environment variable once the connection works.

A tool returns 404 for a resource I know exists

The REST API returns 404 when the caller has no read access, rather than 403, so that nobody can enumerate resources by probing IDs. A 404 on something you can see in the UI usually means the key lacks read access to that space or project, or belongs to a different region. See authorization.

Requests start failing with 429

Rate limits apply per API key, defaulting to 100 requests per minute on a rolling window. An agent paging through a large span set can reach that. Wait for the window to reset, and narrow your filters so fewer pages are needed. See rate limits.

A browser-based client cannot connect

The server rejects requests that carry an Origin header, which means browser clients are blocked by default, including the Inspector web UI. Use the Inspector CLI shown above, or a client that runs as a native process.

A plain GET on the endpoint returns an error

Only the /mcp prefix is routed publicly, and a bare GET or HEAD against it returns a protocol error rather than a health signal. To check reachability, make a tools/list call.

Next steps

Endpoints

Regional URLs for the MCP server.

Authentication

Get an API key and see how bearer token auth works.

Tool catalog

Every tool your agent can now call, with arguments and pagination rules.

Skills

Add the write side: datasets, experiments, evaluators, and prompt optimization.

Skills

MCP server

API reference

API clients

Connect to the AX MCP Server

Add the server to your client

Verify the connection

Troubleshooting

Next steps

Endpoints

Authentication

Tool catalog

Skills

​Add the server to your client

​Verify the connection

​Troubleshooting

​Next steps

Endpoints

Authentication

Tool catalog

Skills

Add the server to your client

Verify the connection

Troubleshooting

Next steps