diff --git a/agents/claude.ts b/agents/claude.ts
index 6a35521..a00a036 100644
--- a/agents/claude.ts
+++ b/agents/claude.ts
@@ -6,7 +6,7 @@ import { agent, installFromNpmTarball } from "./shared.ts";
 
 export const claude = agent({
   name: "claude",
-  inputKey: "anthropic_api_key",
+  inputKeys: ["anthropic_api_key"],
   install: async () => {
     const versionRange = packageJson.dependencies["@anthropic-ai/claude-agent-sdk"] || "latest";
     return await installFromNpmTarball({
diff --git a/agents/codex.ts b/agents/codex.ts
index 6601f41..3506eec 100644
--- a/agents/codex.ts
+++ b/agents/codex.ts
@@ -7,7 +7,7 @@ import { agent, installFromNpmTarball } from "./shared.ts";
 
 export const codex = agent({
   name: "codex",
-  inputKey: "openai_api_key",
+  inputKeys: ["openai_api_key"],
   install: async () => {
     return await installFromNpmTarball({
       packageName: "@openai/codex",
diff --git a/agents/index.ts b/agents/index.ts
index af18fac..b2f2a75 100644
--- a/agents/index.ts
+++ b/agents/index.ts
@@ -8,4 +8,4 @@ export const agents = {
   jules,
 } as const;
 
-export type AgentInputKey = (typeof agents)[keyof typeof agents]["inputKey"];
+export type AgentInputKey = (typeof agents)[keyof typeof agents]["inputKeys"][number];
diff --git a/agents/jules.ts b/agents/jules.ts
index 8dd9af7..9cf68dd 100644
--- a/agents/jules.ts
+++ b/agents/jules.ts
@@ -6,7 +6,7 @@ import { agent, installFromNpmTarball } from "./shared.ts";
 
 export const jules = agent({
   name: "jules",
-  inputKey: "google_api_key",
+  inputKeys: ["google_api_key", "gemini_api_key"],
   install: async () => {
     return await installFromNpmTarball({
       packageName: "@google/jules",
diff --git a/agents/shared.ts b/agents/shared.ts
index 82739b4..22cb0e5 100644
--- a/agents/shared.ts
+++ b/agents/shared.ts
@@ -133,7 +133,7 @@ export const agent = <const agent extends Agent>(agent: agent): agent => {
 
 export type Agent = {
   name: string;
-  inputKey: string;
+  inputKeys: string[];
   install: () => Promise<string>;
   run: (config: AgentConfig) => Promise<AgentResult>;
 };
diff --git a/entry.ts b/entry.ts
index 1dde2de..01e6595 100644
--- a/entry.ts
+++ b/entry.ts
@@ -23,7 +23,9 @@ async function run(): Promise<void> {
     const inputs: Required<Inputs> = {
       prompt: core.getInput("prompt", { required: true }),
       agent: core.getInput("agent") ? AgentName.assert(core.getInput("agent")) : undefined,
-      ...flatMorph(agents, (_, agent) => [agent.inputKey, core.getInput(agent.inputKey)]),
+      ...flatMorph(agents, (_, agent) =>
+        agent.inputKeys.map((inputKey) => [inputKey, core.getInput(inputKey)])
+      ),
     };
 
     const result = await main(inputs);
diff --git a/main.ts b/main.ts
index b06126d..dd09ff4 100644
--- a/main.ts
+++ b/main.ts
@@ -7,6 +7,7 @@ import { fetchRepoSettings } from "./utils/api.ts";
 import { log } from "./utils/cli.ts";
 import {
   parseRepoContext,
+  type RepoContext,
   revokeInstallationToken,
   setupGitHubInstallationToken,
 } from "./utils/github.ts";
@@ -16,13 +17,12 @@ export const AgentName = type.enumerated(...Object.values(agents).map((agent) =>
 export type AgentName = typeof AgentName.infer;
 
 export const AgentInputKey = type.enumerated(
-  ...Object.values(agents).map((agent) => agent.inputKey)
+  ...Object.values(agents).flatMap((agent) => agent.inputKeys)
 );
 export type AgentInputKey = typeof AgentInputKey.infer;
 
-const keyInputDefs = flatMorph(
-  agents,
-  (_, agent) => [agent.inputKey, "string | undefined?"] as const
+const keyInputDefs = flatMorph(agents, (_, agent) =>
+  agent.inputKeys.map((inputKey) => [inputKey, "string | undefined?"] as const)
 );
 
 export const Inputs = type({
@@ -39,7 +39,54 @@ export interface MainResult {
   error?: string | undefined;
 }
 
-export type PromptJSON = {};
+/**
+ * Throw an error for missing API key with helpful message linking to repo settings
+ */
+function throwMissingApiKeyError({
+  agentName,
+  inputKeys,
+  repoContext,
+  inputs,
+}: {
+  agentName: string;
+  inputKeys: string[];
+  repoContext: RepoContext;
+  inputs: Inputs;
+}): never {
+  const apiUrl = process.env.API_URL || "https://pullfrog.ai";
+  const settingsUrl = `${apiUrl}/console/${repoContext.owner}/${repoContext.name}`;
+
+  const secretNames = inputKeys.map((key) => `\`${key.toUpperCase()}\``);
+  const secretNameList =
+    inputKeys.length === 1 ? secretNames[0] : `one of ${secretNames.join(" or ")}`;
+
+  const githubRepoUrl = `https://github.com/${repoContext.owner}/${repoContext.name}`;
+  const githubSecretsUrl = `${githubRepoUrl}/settings/secrets/actions`;
+
+  // Find which agents have inputKeys that match the provided inputs
+  const availableAgents = Object.values(agents).filter((agent) =>
+    agent.inputKeys.some((inputKey) => inputs[inputKey])
+  );
+
+  let message = `Pullfrog is configured to use ${agentName}, but the associated API key was not provided.
+
+To fix this, add the required secret to your GitHub repository:
+
+1. Go to: ${githubSecretsUrl}
+2. Click "New repository secret"
+3. Set the name to ${secretNameList}
+4. Set the value to your API key
+5. Click "Add secret"`;
+
+  // If other credentials are present, suggest alternative agents
+  if (availableAgents.length > 0) {
+    const agentNames = availableAgents.map((agent) => agent.name).join(", ");
+    message += `\n\nAlternatively, configure Pullfrog to use an agent with existing credentials in your environment (${agentNames}) at ${settingsUrl}`;
+  }
+
+  log.error(message);
+  throw new Error(message);
+}
 
 export async function main(inputs: Inputs): Promise<MainResult> {
   let tokenToRevoke: string | null = null;
@@ -81,11 +128,18 @@ export async function main(inputs: Inputs): Promise<MainResult> {
     // if yes, check if it's a webhook payload or toJSON(github.event)
     // for webhook payloads, check the specified `agent` field
 
-    // Get API key based on agent type
+    const matchingInputKey = agent.inputKeys.find((inputKey) => inputs[inputKey]);
 
-    const apiKey = inputs[agent.inputKey];
+    if (!matchingInputKey) {
+      throwMissingApiKeyError({
+        agentName,
+        inputKeys: agent.inputKeys,
+        repoContext,
+        inputs,
+      });
+    }
 
-    if (!apiKey) throw new Error(`${agent.inputKey} is required for ${agentName} agent`);
+    const apiKey = inputs[matchingInputKey]!;
 
     const result = await agent.run({
       prompt: inputs.prompt,
diff --git a/play.ts b/play.ts
index 94d9eec..276111c 100644
--- a/play.ts
+++ b/play.ts
@@ -24,11 +24,10 @@ export async function run(
 
     const inputs: Required<Inputs> = {
       prompt,
-      agent: "jules",
-      ...flatMorph(agents, (_, agent) => [
-        agent.inputKey,
-        process.env[agent.inputKey.toUpperCase()],
-      ]),
+      agent: "claude",
+      ...flatMorph(agents, (_, agent) =>
+        agent.inputKeys.map((inputKey) => [inputKey, process.env[inputKey.toUpperCase()]])
+      ),
     };
 
     const result = await main(inputs);