diff --git a/typescript/.changeset/mainstreet-action-provider.md b/typescript/.changeset/mainstreet-action-provider.md
new file mode 100644
index 000000000..b6833895c
--- /dev/null
+++ b/typescript/.changeset/mainstreet-action-provider.md
@@ -0,0 +1,5 @@
+---
+"@coinbase/agentkit": patch
+---
+
+Add MainStreet action provider: `check_reputation` returns an onchain-verifiable SAFE/CAUTION/BLOCK reputation verdict + 0–100 score for a Base counterparty before payment, so an agent can refuse to pay BLOCK-rated or unscored addresses.
diff --git a/typescript/agentkit/README.md b/typescript/agentkit/README.md
index 37b14207f..4df8d70e7 100644
--- a/typescript/agentkit/README.md
+++ b/typescript/agentkit/README.md
@@ -485,6 +485,15 @@ const agent = createAgent({
 </table>
 </details>
 <details>
+<summary><strong>MainStreet</strong></summary>
+<table width="100%">
+<tr>
+    <td width="200"><code>check_reputation</code></td>
+    <td width="768">Returns an onchain-verifiable SAFE/CAUTION/BLOCK reputation verdict + 0-100 score for a Base wallet, agent, or token before payment, so an agent can refuse to pay BLOCK-rated or unscored counterparties.</td>
+</tr>
+</table>
+</details>
+<details>
 <summary><strong>Messari</strong></summary>
 <table width="100%">
 <tr>
diff --git a/typescript/agentkit/src/action-providers/index.ts b/typescript/agentkit/src/action-providers/index.ts
index 9f7164086..486e286d5 100644
--- a/typescript/agentkit/src/action-providers/index.ts
+++ b/typescript/agentkit/src/action-providers/index.ts
@@ -18,6 +18,7 @@ export * from "./erc721";
 export * from "./erc8004";
 export * from "./farcaster";
 export * from "./jupiter";
+export * from "./mainstreet";
 export * from "./messari";
 export * from "./pyth";
 export * from "./moonwell";
diff --git a/typescript/agentkit/src/action-providers/mainstreet/README.md b/typescript/agentkit/src/action-providers/mainstreet/README.md
new file mode 100644
index 000000000..e03eac835
--- /dev/null
+++ b/typescript/agentkit/src/action-providers/mainstreet/README.md
@@ -0,0 +1,26 @@
+# MainStreet Action Provider
+
+This directory contains the **MainStreetActionProvider** — an onchain reputation check for a Base
+counterparty before an agent transacts or pays it (e.g. via x402).
+
+[MainStreet](https://avisradar-production.up.railway.app/mainstreet.html) is an onchain reputation
+oracle for agent-to-agent payments on Base. For any wallet, agent, or token it returns a
+SAFE / CAUTION / BLOCK verdict + a 0–100 score as an **EIP-712-signed attestation, verifiable onchain**
+against the MainStreetVerifier contract (`0x7397adb9713934c36d22aa54b4dbbcd70263592b`) — the signal is
+checkable, not "trust us". Free, no signup (100 checks/day/IP).
+
+## Actions
+
+- `check_reputation`: Returns the reputation verdict + score for a Base address, with a pay / don't-pay
+  recommendation and a link to verify the signed attestation. Use it as a pre-payment / pre-routing
+  trust gate — refuse to settle to a BLOCK-rated or unscored counterparty.
+
+## Usage
+
+```typescript
+import { mainstreetActionProvider } from "@coinbase/agentkit";
+
+const provider = mainstreetActionProvider();
+```
+
+No configuration required (public read API). Pairs naturally with the `x402` and `erc8004` providers.
diff --git a/typescript/agentkit/src/action-providers/mainstreet/index.ts b/typescript/agentkit/src/action-providers/mainstreet/index.ts
new file mode 100644
index 000000000..53cc04459
--- /dev/null
+++ b/typescript/agentkit/src/action-providers/mainstreet/index.ts
@@ -0,0 +1 @@
+export * from "./mainstreetActionProvider";
diff --git a/typescript/agentkit/src/action-providers/mainstreet/mainstreetActionProvider.test.ts b/typescript/agentkit/src/action-providers/mainstreet/mainstreetActionProvider.test.ts
new file mode 100644
index 000000000..73f720d4f
--- /dev/null
+++ b/typescript/agentkit/src/action-providers/mainstreet/mainstreetActionProvider.test.ts
@@ -0,0 +1,69 @@
+import { mainstreetActionProvider } from "./mainstreetActionProvider";
+
+describe("MainStreetActionProvider", () => {
+  const fetchMock = jest.fn();
+  global.fetch = fetchMock;
+
+  const provider = mainstreetActionProvider();
+  const ADDR = "0x325bdf6f7efab24a2210c48c1b64cab2eae1d430";
+
+  beforeEach(() => {
+    jest.resetAllMocks();
+  });
+
+  describe("checkReputation", () => {
+    it("recommends proceeding for a SAFE counterparty with a real score", async () => {
+      fetchMock.mockResolvedValue({
+        ok: true,
+        json: jest.fn().mockResolvedValue({ score: 76, verdict: "SAFE" }),
+      });
+
+      const result = JSON.parse(await provider.checkReputation({ address: ADDR }));
+      expect(result.score).toBe(76);
+      expect(result.verdict).toBe("SAFE");
+      expect(result.recommendation).toContain("OK to proceed");
+    });
+
+    it("refuses to pay a BLOCK-rated counterparty", async () => {
+      fetchMock.mockResolvedValue({
+        ok: true,
+        json: jest.fn().mockResolvedValue({ score: 10, verdict: "BLOCK" }),
+      });
+
+      const result = JSON.parse(await provider.checkReputation({ address: ADDR }));
+      expect(result.recommendation).toContain("DO NOT PAY");
+    });
+
+    it("treats an unknown / unscored counterparty as CAUTION (never auto-OK)", async () => {
+      fetchMock.mockResolvedValue({
+        ok: true,
+        json: jest.fn().mockResolvedValue({ score: null, verdict: null }),
+      });
+
+      const result = JSON.parse(await provider.checkReputation({ address: ADDR }));
+      expect(result.recommendation).toContain("CAUTION");
+    });
+
+    it("handles HTTP errors gracefully", async () => {
+      fetchMock.mockResolvedValue({ ok: false, status: 404 });
+
+      const result = await provider.checkReputation({ address: ADDR });
+      expect(result).toContain("MainStreet error");
+      expect(result).toContain("404");
+    });
+
+    it("handles network errors gracefully", async () => {
+      fetchMock.mockRejectedValue(new Error("Network error"));
+
+      const result = await provider.checkReputation({ address: ADDR });
+      expect(result).toContain("MainStreet error");
+      expect(result).toContain("Network error");
+    });
+  });
+
+  describe("supportsNetwork", () => {
+    it("supports any network (network-agnostic API call)", () => {
+      expect(provider.supportsNetwork()).toBe(true);
+    });
+  });
+});
diff --git a/typescript/agentkit/src/action-providers/mainstreet/mainstreetActionProvider.ts b/typescript/agentkit/src/action-providers/mainstreet/mainstreetActionProvider.ts
new file mode 100644
index 000000000..d5e0d43b8
--- /dev/null
+++ b/typescript/agentkit/src/action-providers/mainstreet/mainstreetActionProvider.ts
@@ -0,0 +1,101 @@
+import { z } from "zod";
+import { ActionProvider } from "../actionProvider";
+import { CreateAction } from "../actionDecorator";
+import { CheckReputationSchema } from "./schemas";
+
+const MAINSTREET_BASE_URL = "https://avisradar-production.up.railway.app";
+
+/**
+ * MainStreetActionProvider lets an agent check the onchain reputation of a Base
+ * counterparty BEFORE it transacts or pays via x402.
+ *
+ * MainStreet is an onchain reputation oracle for agent-to-agent payments on Base:
+ * for any wallet, agent, or token it returns a SAFE / CAUTION / BLOCK verdict + a
+ * 0-100 score as an EIP-712-signed attestation, verifiable onchain against the
+ * MainStreetVerifier contract on Base (0x7397adb9713934c36d22aa54b4dbbcd70263592b) —
+ * so the trust signal is checkable, not "trust us". Network-agnostic API call.
+ */
+export class MainStreetActionProvider extends ActionProvider {
+  /**
+   * Constructor for the MainStreetActionProvider class.
+   */
+  constructor() {
+    super("mainstreet", []);
+  }
+
+  /**
+   * Checks the onchain reputation of a Base wallet / agent / token deployer.
+   *
+   * @param args - The address to check.
+   * @returns A JSON string with the score, verdict, a pay/don't-pay recommendation, and a verify link.
+   */
+  @CreateAction({
+    name: "check_reputation",
+    description: `Check the onchain reputation of a Base wallet, agent, or token deployer BEFORE paying or transacting with it.
+Returns a SAFE / CAUTION / BLOCK verdict + a 0-100 score from MainStreet, an onchain reputation oracle for agent-to-agent payments on Base.
+Use this as a pre-payment / pre-routing trust gate: refuse to settle to a BLOCK-rated or low-scoring counterparty.
+Takes the following input:
+- address: the 0x Base address to check.
+Notes:
+- Free, no signup (100 checks/day/IP).
+- The verdict is backed by settlement history, endpoint health, ERC-8004 feedback and identity proofs, and is EIP-712-signed + verifiable onchain against the MainStreetVerifier contract.`,
+    schema: CheckReputationSchema,
+  })
+  async checkReputation(args: z.infer<typeof CheckReputationSchema>): Promise<string> {
+    try {
+      const url = `${MAINSTREET_BASE_URL}/api/agent/score/${args.address}`;
+      const response = await fetch(url, { headers: { accept: "application/json" } });
+
+      if (!response.ok) {
+        return `MainStreet error: HTTP ${response.status} checking ${args.address}`;
+      }
+
+      const data = (await response.json()) as {
+        score?: number | null;
+        verdict?: string | null;
+        trustLevel?: string | null;
+      };
+      const score = data.score ?? null;
+      const verdict = data.verdict ?? data.trustLevel ?? "UNKNOWN";
+
+      // Safe default: only green-light a known SAFE counterparty with a real score.
+      // An unknown / unscored address (no reputation history — e.g. a fresh wallet)
+      // must NOT default to "OK", or the gate is useless against new scam wallets.
+      const recommendation =
+        verdict === "BLOCK" || (typeof score === "number" && score < 30)
+          ? "DO NOT PAY — BLOCK-rated or below a safe threshold."
+          : verdict === "SAFE" && typeof score === "number" && score >= 30
+            ? "OK to proceed — counterparty looks trustworthy."
+            : "CAUTION — no / insufficient reputation history; verify before paying.";
+
+      return JSON.stringify({
+        address: args.address,
+        score,
+        verdict,
+        recommendation,
+        verify: `${MAINSTREET_BASE_URL}/api/agent/attestation/${args.address}`,
+        source:
+          "MainStreet — onchain reputation oracle on Base (EIP-712 signed, verifiable against MainStreetVerifier 0x7397adb9713934c36d22aa54b4dbbcd70263592b).",
+      });
+    } catch (error) {
+      return `MainStreet error: ${error instanceof Error ? error.message : String(error)}`;
+    }
+  }
+
+  /**
+   * Checks if the MainStreet action provider supports the given network.
+   * MainStreet scores Base addresses but the lookup is a network-agnostic API call.
+   *
+   * @returns True — MainStreet actions are callable from any network context.
+   */
+  supportsNetwork(): boolean {
+    return true;
+  }
+}
+
+/**
+ * Creates a new instance of the MainStreet action provider.
+ *
+ * @returns A new MainStreetActionProvider instance.
+ */
+export const mainstreetActionProvider = () => new MainStreetActionProvider();
diff --git a/typescript/agentkit/src/action-providers/mainstreet/schemas.ts b/typescript/agentkit/src/action-providers/mainstreet/schemas.ts
new file mode 100644
index 000000000..be4930025
--- /dev/null
+++ b/typescript/agentkit/src/action-providers/mainstreet/schemas.ts
@@ -0,0 +1,13 @@
+import { z } from "zod";
+
+/**
+ * Input schema for checking the MainStreet onchain reputation of a Base address.
+ */
+export const CheckReputationSchema = z
+  .object({
+    address: z
+      .string()
+      .regex(/^0x[a-fA-F0-9]{40}$/, "must be a 0x-prefixed 40-hex Base address")
+      .describe("The Base wallet, agent, or token-deployer address to check (0x...)."),
+  })
+  .strict();