> ## Documentation Index
> Fetch the complete documentation index at: https://docs.voiceflow.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Developer surfaces

> Tokens, traces, the CLI and MCP: the vocabulary for driving Voiceflow over HTTP, including the one credential that is not the others.

| Term                                                       | What it is                                                                                                                                 |
| ---------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------ |
| **[Personal access token](/api-reference/authentication)** | The credential for the REST API, the `vf` CLI and the MCP server. One token, three surfaces.                                               |
| **Session key**                                            | A separate credential, from the start-session endpoint, used **only** by `/v4/interact`. Passing an API key there returns 401.             |
| **[Trace](/api-reference/trace-types)**                    | One item in an agent's reply: text, a card, a debug note. A turn returns an array of them.                                                 |
| **[CLI](/cli/overview)**                                   | `vf`, the command-line client. Generated from the same OpenAPI spec as the REST API.                                                       |
| **[MCP server](/mcp/overview)**                            | A Model Context Protocol server whose tools an agent can call. Its tools are populated by syncing the server, not created by hand.         |
| **Conversation state**                                     | The stored state of a live conversation: where it stands and what its variables hold. Separate from the transcript, which is the record.   |
| **MCP tool**                                               | A tool an MCP server advertises. Populated by syncing the server rather than created by hand, so the list mirrors what the server exposes. |