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Add x402/MPP auto-payment to MCP server tools
New paid-fetch module reads the local allowance and wraps fetch with @x402/fetch (Base USDC) or mppx (Tempo pathUSD) payment interceptor. Six MCP tools now pay automatically on 402 instead of returning informational text — matching CLI behavior. Falls back gracefully when no allowance is configured. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
1 parent 6fe68b1 commit c5d548e

8 files changed

Lines changed: 278 additions & 12 deletions

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src/paid-fetch.test.ts

Lines changed: 120 additions & 0 deletions
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import { describe, it, beforeEach, afterEach, mock } from "node:test";
2+
import assert from "node:assert/strict";
3+
import { mkdtempSync, writeFileSync, rmSync } from "node:fs";
4+
import { join } from "node:path";
5+
import { tmpdir } from "node:os";
6+
7+
const originalFetch = globalThis.fetch;
8+
let tempDir: string;
9+
10+
beforeEach(() => {
11+
tempDir = mkdtempSync(join(tmpdir(), "run402-paid-fetch-test-"));
12+
process.env.RUN402_CONFIG_DIR = tempDir;
13+
process.env.RUN402_API_BASE = "https://test-api.run402.com";
14+
});
15+
16+
afterEach(() => {
17+
globalThis.fetch = originalFetch;
18+
rmSync(tempDir, { recursive: true, force: true });
19+
delete process.env.RUN402_CONFIG_DIR;
20+
delete process.env.RUN402_API_BASE;
21+
});
22+
23+
describe("setupPaidFetch", () => {
24+
it("returns null when no allowance file exists", async () => {
25+
const { setupPaidFetch, _resetPaidFetchCache } = await import(`./paid-fetch.js?t=${Date.now()}`);
26+
_resetPaidFetchCache();
27+
const result = await setupPaidFetch();
28+
assert.equal(result, null);
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});
30+
31+
it("returns null when allowance exists but payment libs fail to import", async () => {
32+
// Write an allowance file so readAllowance succeeds
33+
writeFileSync(
34+
join(tempDir, "allowance.json"),
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JSON.stringify({
36+
address: "0x1234567890abcdef1234567890abcdef12345678",
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privateKey: "0xac0974bec39a17e36ba4a6b4d238ff944bacb478cbed5efcae784d7bf4f2ff80",
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created: "2026-01-01T00:00:00Z",
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funded: true,
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rail: "x402",
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}),
42+
);
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// The test environment doesn't have @x402/fetch etc. installed as real modules,
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// so setupPaidFetch should catch the import error and return null
46+
const { setupPaidFetch, _resetPaidFetchCache } = await import(`./paid-fetch.js?t=${Date.now()}`);
47+
_resetPaidFetchCache();
48+
const result = await setupPaidFetch();
49+
// May be null (import fails) or a function (if libs are available in dev)
50+
assert.ok(result === null || typeof result === "function");
51+
});
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});
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54+
describe("paidApiRequest", () => {
55+
it("falls back to bare apiRequest when no allowance", async () => {
56+
// No allowance file → paidApiRequest should just call apiRequest
57+
globalThis.fetch = (async () =>
58+
new Response(JSON.stringify({ ok: true }), {
59+
status: 200,
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headers: { "Content-Type": "application/json" },
61+
})) as typeof fetch;
62+
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const { paidApiRequest, _resetPaidFetchCache } = await import(`./paid-fetch.js?t=${Date.now()}`);
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_resetPaidFetchCache();
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const result = await paidApiRequest("/test");
66+
assert.equal(result.ok, true);
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assert.equal(result.status, 200);
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});
69+
70+
it("returns is402 when no paid fetch and server returns 402", async () => {
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// No allowance → no paid fetch → 402 passes through
72+
globalThis.fetch = (async () =>
73+
new Response(
74+
JSON.stringify({ x402: { price: "$0.10" } }),
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{ status: 402, headers: { "Content-Type": "application/json" } },
76+
)) as typeof fetch;
77+
78+
const { paidApiRequest, _resetPaidFetchCache } = await import(`./paid-fetch.js?t=${Date.now()}`);
79+
_resetPaidFetchCache();
80+
const result = await paidApiRequest("/test");
81+
assert.equal(result.ok, false);
82+
assert.equal(result.is402, true);
83+
assert.equal(result.status, 402);
84+
});
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86+
it("caches setupPaidFetch result across calls", async () => {
87+
globalThis.fetch = (async () =>
88+
new Response(JSON.stringify({ ok: true }), {
89+
status: 200,
90+
headers: { "Content-Type": "application/json" },
91+
})) as typeof fetch;
92+
93+
const mod = await import(`./paid-fetch.js?t=${Date.now()}`);
94+
mod._resetPaidFetchCache();
95+
96+
// First call initializes cache
97+
await mod.paidApiRequest("/test1");
98+
// Second call should reuse cache (no re-initialization)
99+
await mod.paidApiRequest("/test2");
100+
101+
// If we got here without error, caching works
102+
assert.ok(true);
103+
});
104+
105+
it("restores globalThis.fetch after call", async () => {
106+
const myFetch = (async () =>
107+
new Response(JSON.stringify({ ok: true }), {
108+
status: 200,
109+
headers: { "Content-Type": "application/json" },
110+
})) as typeof fetch;
111+
globalThis.fetch = myFetch;
112+
113+
const { paidApiRequest, _resetPaidFetchCache } = await import(`./paid-fetch.js?t=${Date.now()}`);
114+
_resetPaidFetchCache();
115+
await paidApiRequest("/test");
116+
117+
// globalThis.fetch should be restored to our myFetch
118+
assert.equal(globalThis.fetch, myFetch);
119+
});
120+
});

src/paid-fetch.ts

Lines changed: 92 additions & 0 deletions
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@@ -0,0 +1,92 @@
1+
/**
2+
* Paid fetch for MCP server — reads the local allowance, branches on rail
3+
* (x402 vs mpp), returns a wrapped fetch that intercepts 402 responses,
4+
* signs payment, and retries automatically.
5+
*
6+
* Returns null when no allowance is configured or payment libraries are
7+
* unavailable (graceful degradation).
8+
*/
9+
10+
import { readAllowance } from "./allowance.js";
11+
import { apiRequest } from "./client.js";
12+
import type { ApiResponse, ApiRequestOptions } from "./client.js";
13+
14+
type FetchFn = typeof globalThis.fetch;
15+
16+
/**
17+
* Create a payment-wrapping fetch function from the local allowance.
18+
* Returns null if no allowance exists or payment libraries fail to load.
19+
*/
20+
export async function setupPaidFetch(): Promise<FetchFn | null> {
21+
const allowance = readAllowance();
22+
if (!allowance) return null;
23+
24+
try {
25+
if (allowance.rail === "mpp") {
26+
// mppx is an optional peer — use variable to skip TS module resolution
27+
const mppxMod = "mppx/client";
28+
const { Mppx, tempo }: any = await import(/* webpackIgnore: true */ mppxMod);
29+
const { privateKeyToAccount } = await import("viem/accounts");
30+
const account = privateKeyToAccount(allowance.privateKey as `0x${string}`);
31+
const mppx = Mppx.create({
32+
polyfill: false,
33+
methods: [tempo({ account })],
34+
});
35+
return mppx.fetch as FetchFn;
36+
}
37+
38+
// Default: x402
39+
const { privateKeyToAccount } = await import("viem/accounts");
40+
const { createPublicClient, http } = await import("viem");
41+
const { base, baseSepolia } = await import("viem/chains");
42+
const { x402Client, wrapFetchWithPayment } = await import("@x402/fetch");
43+
const { ExactEvmScheme } = await import("@x402/evm/exact/client");
44+
const { toClientEvmSigner } = await import("@x402/evm");
45+
46+
const account = privateKeyToAccount(allowance.privateKey as `0x${string}`);
47+
const mainnetClient = createPublicClient({ chain: base, transport: http() });
48+
const sepoliaClient = createPublicClient({ chain: baseSepolia, transport: http() });
49+
50+
const client = new x402Client();
51+
client.register("eip155:8453", new ExactEvmScheme(toClientEvmSigner(account, mainnetClient)));
52+
client.register("eip155:84532", new ExactEvmScheme(toClientEvmSigner(account, sepoliaClient)));
53+
54+
return wrapFetchWithPayment(fetch, client) as FetchFn;
55+
} catch {
56+
// Payment libraries not available — degrade gracefully
57+
return null;
58+
}
59+
}
60+
61+
/** Cached paid fetch — initialized lazily on first call */
62+
let cachedPaidFetch: FetchFn | null | undefined;
63+
64+
/**
65+
* Like apiRequest, but uses the paid fetch wrapper when available.
66+
* Falls back to bare apiRequest when no allowance is configured.
67+
*/
68+
export async function paidApiRequest(
69+
path: string,
70+
opts: ApiRequestOptions = {},
71+
): Promise<ApiResponse> {
72+
if (cachedPaidFetch === undefined) {
73+
cachedPaidFetch = await setupPaidFetch();
74+
}
75+
76+
if (!cachedPaidFetch) {
77+
return apiRequest(path, opts);
78+
}
79+
80+
const originalFetch = globalThis.fetch;
81+
globalThis.fetch = cachedPaidFetch;
82+
try {
83+
return await apiRequest(path, opts);
84+
} finally {
85+
globalThis.fetch = originalFetch;
86+
}
87+
}
88+
89+
/** Reset cached state — exposed for testing only */
90+
export function _resetPaidFetchCache(): void {
91+
cachedPaidFetch = undefined;
92+
}

src/tools/bundle-deploy.ts

Lines changed: 29 additions & 2 deletions
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@@ -1,5 +1,5 @@
11
import { z } from "zod";
2-
import { apiRequest } from "../client.js";
2+
import { paidApiRequest } from "../paid-fetch.js";
33
import { formatApiError, projectNotFound } from "../errors.js";
44
import { requireAllowanceAuth } from "../allowance-auth.js";
55
import { getProject } from "../keystore.js";
@@ -74,7 +74,7 @@ export async function handleBundleDeploy(args: {
7474
const auth = requireAllowanceAuth("/deploy/v1");
7575
if ("error" in auth) return auth.error;
7676

77-
const res = await apiRequest("/deploy/v1", {
77+
const res = await paidApiRequest("/deploy/v1", {
7878
method: "POST",
7979
headers: { ...auth.headers },
8080
body: {
@@ -88,6 +88,33 @@ export async function handleBundleDeploy(args: {
8888
},
8989
});
9090

91+
if (res.is402) {
92+
const body = res.body as Record<string, unknown>;
93+
const lines = [
94+
`## Payment Required`,
95+
``,
96+
`To deploy this bundle, an x402 payment is needed.`,
97+
``,
98+
];
99+
if (body.x402) {
100+
lines.push(`**Payment details:**`);
101+
lines.push("```json");
102+
lines.push(JSON.stringify(body.x402, null, 2));
103+
lines.push("```");
104+
} else {
105+
lines.push(`**Server response:**`);
106+
lines.push("```json");
107+
lines.push(JSON.stringify(body, null, 2));
108+
lines.push("```");
109+
}
110+
lines.push(``);
111+
lines.push(
112+
`The user's agent allowance or payment agent must send the required amount. ` +
113+
`Once payment is confirmed, retry this tool call.`,
114+
);
115+
return { content: [{ type: "text", text: lines.join("\n") }] };
116+
}
117+
91118
if (!res.ok) return formatApiError(res, "deploying bundle");
92119

93120
const body = res.body as {

src/tools/deploy-function.ts

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -1,5 +1,5 @@
11
import { z } from "zod";
2-
import { apiRequest } from "../client.js";
2+
import { paidApiRequest } from "../paid-fetch.js";
33
import { getProject } from "../keystore.js";
44
import { formatApiError, projectNotFound } from "../errors.js";
55

@@ -34,7 +34,7 @@ export async function handleDeployFunction(args: {
3434
const project = getProject(args.project_id);
3535
if (!project) return projectNotFound(args.project_id);
3636

37-
const res = await apiRequest(`/projects/v1/admin/${args.project_id}/functions`, {
37+
const res = await paidApiRequest(`/projects/v1/admin/${args.project_id}/functions`, {
3838
method: "POST",
3939
headers: {
4040
Authorization: `Bearer ${project.service_key}`,

src/tools/generate-image.ts

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -1,5 +1,5 @@
11
import { z } from "zod";
2-
import { apiRequest } from "../client.js";
2+
import { paidApiRequest } from "../paid-fetch.js";
33
import { formatApiError } from "../errors.js";
44

55
export const generateImageSchema = {
@@ -21,7 +21,7 @@ export async function handleGenerateImage(args: {
2121
}> {
2222
const aspect = args.aspect || "square";
2323

24-
const res = await apiRequest("/generate-image/v1", {
24+
const res = await paidApiRequest("/generate-image/v1", {
2525
method: "POST",
2626
body: { prompt: args.prompt, aspect },
2727
});

src/tools/invoke-function.ts

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -1,5 +1,5 @@
11
import { z } from "zod";
2-
import { apiRequest } from "../client.js";
2+
import { paidApiRequest } from "../paid-fetch.js";
33
import { getProject } from "../keystore.js";
44
import { formatApiError, projectNotFound } from "../errors.js";
55

@@ -38,7 +38,7 @@ export async function handleInvokeFunction(args: {
3838

3939
const startTime = Date.now();
4040

41-
const res = await apiRequest(`/functions/v1/${args.name}`, {
41+
const res = await paidApiRequest(`/functions/v1/${args.name}`, {
4242
method,
4343
headers: requestHeaders,
4444
body: method !== "GET" && method !== "HEAD" ? args.body : undefined,

src/tools/provision.ts

Lines changed: 29 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -1,5 +1,5 @@
11
import { z } from "zod";
2-
import { apiRequest } from "../client.js";
2+
import { paidApiRequest } from "../paid-fetch.js";
33
import { saveProject, setActiveProjectId } from "../keystore.js";
44
import { formatApiError } from "../errors.js";
55
import { requireAllowanceAuth } from "../allowance-auth.js";
@@ -25,12 +25,39 @@ export async function handleProvision(args: {
2525
const tier = args.tier || "prototype";
2626
const name = args.name;
2727

28-
const res = await apiRequest("/projects/v1", {
28+
const res = await paidApiRequest("/projects/v1", {
2929
method: "POST",
3030
headers: { ...auth.headers },
3131
body: { tier, name },
3232
});
3333

34+
if (res.is402) {
35+
const body = res.body as Record<string, unknown>;
36+
const lines = [
37+
`## Payment Required`,
38+
``,
39+
`To provision a **${tier}** project, an x402 payment is needed.`,
40+
``,
41+
];
42+
if (body.x402) {
43+
lines.push(`**Payment details:**`);
44+
lines.push("```json");
45+
lines.push(JSON.stringify(body.x402, null, 2));
46+
lines.push("```");
47+
} else {
48+
lines.push(`**Server response:**`);
49+
lines.push("```json");
50+
lines.push(JSON.stringify(body, null, 2));
51+
lines.push("```");
52+
}
53+
lines.push(``);
54+
lines.push(
55+
`The user's agent allowance or payment agent must send the required amount. ` +
56+
`Once payment is confirmed, retry this tool call.`,
57+
);
58+
return { content: [{ type: "text", text: lines.join("\n") }] };
59+
}
60+
3461
if (!res.ok) return formatApiError(res, "provisioning project");
3562

3663
const body = res.body as {

src/tools/set-tier.ts

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -1,5 +1,5 @@
11
import { z } from "zod";
2-
import { apiRequest } from "../client.js";
2+
import { paidApiRequest } from "../paid-fetch.js";
33
import { formatApiError } from "../errors.js";
44

55
export const setTierSchema = {
@@ -11,7 +11,7 @@ export const setTierSchema = {
1111
export async function handleSetTier(args: {
1212
tier: string;
1313
}): Promise<{ content: Array<{ type: "text"; text: string }>; isError?: boolean }> {
14-
const res = await apiRequest(`/tiers/v1/${args.tier}`, {
14+
const res = await paidApiRequest(`/tiers/v1/${args.tier}`, {
1515
method: "POST",
1616
body: {},
1717
});

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