diff --git a/packages/sdk/src/types.ts b/packages/sdk/src/types.ts
index c9b782d82..f9062bbeb 100644
--- a/packages/sdk/src/types.ts
+++ b/packages/sdk/src/types.ts
@@ -19,8 +19,13 @@ export interface SpawnPtyInput {
   restartPolicy?: RestartPolicy;
   continueFrom?: string;
   skipRelayPrompt?: boolean;
-  /** JWT token for relayauth/relayfile permissions. When set, the broker
-   *  injects RELAY_AGENT_TOKEN into the agent's environment. */
+  /** Optional pre-minted relaycast agent token (`at_live_<hex>`, from
+   *  `registerAgent(workspaceKey, name)` in `@agent-relay/sdk/http`). The
+   *  broker plumbs this as `RELAY_AGENT_TOKEN`, which the relaycast MCP
+   *  authenticates with. When omitted, the relaycast MCP auto-mints a token
+   *  using `RELAY_API_KEY` + the spawn name; that is the recommended path.
+   *  Note: this is a relaycast credential, NOT a relayfile/relayauth token —
+   *  override `env.RELAYFILE_TOKEN` on the constructor for relayfile auth. */
   agentToken?: string;
 }
 
@@ -31,8 +36,13 @@ export interface SpawnHeadlessInput {
   channels?: string[];
   task?: string;
   skipRelayPrompt?: boolean;
-  /** JWT token for relayauth/relayfile permissions. When set, the broker
-   *  injects RELAY_AGENT_TOKEN into the agent's environment. */
+  /** Optional pre-minted relaycast agent token (`at_live_<hex>`, from
+   *  `registerAgent(workspaceKey, name)` in `@agent-relay/sdk/http`). The
+   *  broker plumbs this as `RELAY_AGENT_TOKEN`, which the relaycast MCP
+   *  authenticates with. When omitted, the relaycast MCP auto-mints a token
+   *  using `RELAY_API_KEY` + the spawn name; that is the recommended path.
+   *  Note: this is a relaycast credential, NOT a relayfile/relayauth token —
+   *  override `env.RELAYFILE_TOKEN` on the constructor for relayfile auth. */
   agentToken?: string;
 }
 
@@ -54,8 +64,13 @@ export interface SpawnProviderInput {
   restartPolicy?: RestartPolicy;
   continueFrom?: string;
   skipRelayPrompt?: boolean;
-  /** JWT token for relayauth/relayfile permissions. When set, the broker
-   *  injects RELAY_AGENT_TOKEN into the agent's environment. */
+  /** Optional pre-minted relaycast agent token (`at_live_<hex>`, from
+   *  `registerAgent(workspaceKey, name)` in `@agent-relay/sdk/http`). The
+   *  broker plumbs this as `RELAY_AGENT_TOKEN`, which the relaycast MCP
+   *  authenticates with. When omitted, the relaycast MCP auto-mints a token
+   *  using `RELAY_API_KEY` + the spawn name; that is the recommended path.
+   *  Note: this is a relaycast credential, NOT a relayfile/relayauth token —
+   *  override `env.RELAYFILE_TOKEN` on the constructor for relayfile auth. */
   agentToken?: string;
 }