diff --git a/packages/loopover-mcp/bin/loopover-mcp.js b/packages/loopover-mcp/bin/loopover-mcp.js
index 9aca87cabe..7d396cc12f 100755
--- a/packages/loopover-mcp/bin/loopover-mcp.js
+++ b/packages/loopover-mcp/bin/loopover-mcp.js
@@ -636,6 +636,36 @@ const simulateOpenPrPressureShape = {
   contributorOpenPrCount: simulateOpenPrPressureCount.optional(),
 };
 
+// #6748: mirrors checkImprovementPotentialShape in src/mcp/server.ts VERBATIM. The bin cannot import from
+// src/ (package boundary), so this is the one copy parity rests on by convention — its own tests pin that the
+// bounds the real schema enforces are enforced here too, rather than waved through to a route 400.
+const checkImprovementPotentialShape = {
+  changedFiles: z
+    .array(z.object({ path: z.string().min(1).max(400), additions: z.number().int().min(0).optional(), deletions: z.number().int().min(0).optional() }))
+    .max(2000)
+    .optional(),
+  tests: z.array(z.string().max(400)).max(2000).optional(),
+  testFiles: z.array(z.string().max(400)).max(2000).optional(),
+  patchCoverageDeltaPercent: z.number().optional(),
+  complexityDeltas: z
+    .array(
+      z.object({
+        file: z.string().min(1).max(400),
+        line: z.number().int().min(1),
+        name: z.string().min(1).max(400),
+        before: z.number().int().min(0),
+        after: z.number().int().min(0),
+        delta: z.number().int(),
+      }),
+    )
+    .max(2000)
+    .optional(),
+  duplicationDeltas: z
+    .array(z.object({ file: z.string().min(1).max(400), line: z.number().int().min(1), duplicateOfLine: z.number().int().min(1), lines: z.number().int().min(1) }))
+    .max(2000)
+    .optional(),
+};
+
 const checkSlopRiskShape = {
   changedFiles: z
     .array(z.object({ path: z.string().min(1).max(400), additions: z.number().int().min(0).optional(), deletions: z.number().int().min(0).optional() }))
@@ -945,6 +975,12 @@ const STDIO_TOOL_DESCRIPTORS = [
     category: "review",
     description: "Assess the deterministic slop risk of a planned change from local diff metadata (paths + line counts) + the PR description — an agent-native, source-free quality self-check. Returns slopRisk (0-100), band, findings, and the rubric. Computed in-process; no repo data and no API round-trip.",
   },
+  {
+    name: "loopover_check_improvement_potential",
+    category: "review",
+    description:
+      "Assess a planned change's deterministic structural-improvement potential from local diff metadata alone (no source uploaded) — reduced complexity, resolved duplication, patch-coverage delta, added test evidence. Returns improvementScore (0-100), band, and findings. The positive-axis counterpart to check_slop_risk; advisory-only, never blocks.",
+  },
   {
     name: "loopover_simulate_open_pr_pressure",
     category: "discovery",
@@ -1541,6 +1577,19 @@ registerStdioTool(
   (input) => toolResult("LoopOver slop-risk self-check.", { ...buildSlopAssessment(input), rubric: SLOP_RUBRIC_MARKDOWN }),
 );
 
+// #6748: CLI mirror of the remote server's loopover_check_improvement_potential. Proxies rather than computing
+// in-process (like the boundary-tests / open-PR-pressure mirrors): buildStructuralImprovementAssessment lives
+// app-side in src/signals/improvement.ts, not in @loopover/engine, so POST /v1/lint/improvement-potential stays
+// the single source of truth for the scoring.
+registerStdioTool(
+  "loopover_check_improvement_potential",
+  {
+    description: stdioToolDescription("loopover_check_improvement_potential"),
+    inputSchema: checkImprovementPotentialShape,
+  },
+  async (input) => toolResult("LoopOver improvement-potential self-check.", await apiPost("/v1/lint/improvement-potential", input)),
+);
+
 // #6751: CLI mirror of the remote server's loopover_simulate_open_pr_pressure. Proxies rather than computing
 // in-process (like the boundary-tests mirror, #6750): simulateOpenPrPressure lives app-side in
 // src/services/open-pr-pressure-scenarios.ts, not in @loopover/engine, so POST /v1/lint/open-pr-pressure stays
diff --git a/src/api/routes.ts b/src/api/routes.ts
index 22f558ff56..baf0fc7e4d 100644
--- a/src/api/routes.ts
+++ b/src/api/routes.ts
@@ -155,6 +155,8 @@ import {
 } from "../orb/relay";
 import { computeFleetAnalytics } from "../orb/analytics";
 import { handleMcpRequest } from "../mcp/server";
+import { checkImprovementPotentialShape } from "../mcp/server";
+import { buildStructuralImprovementAssessment } from "../signals/improvement";
 import { simulateOpenPrPressureShape } from "../mcp/server";
 import { simulateOpenPrPressure, type OpenPrPressureInput } from "../services/open-pr-pressure-scenarios";
 import { buildOpenApiSpec } from "../openapi/spec";
@@ -3292,6 +3294,19 @@ export function createApp() {
     return c.json({ ...buildSlopAssessment(parsed.data), rubric: SLOP_RUBRIC_MARKDOWN });
   });
 
+  // #6748: REST mirror of the loopover_check_improvement_potential MCP tool — deterministic, rate-limit-only,
+  // pure local-metadata, the same tier as the /v1/lint/* routes it sits with. Parses with the tool's OWN
+  // exported checkImprovementPotentialShape so the two surfaces cannot diverge on accepted input, then returns
+  // the SAME field subset the tool's handler returns (improvementScore/band/findings) rather than the whole
+  // assessment, so the mirror is byte-identical to the tool rather than merely similar.
+  app.post("/v1/lint/improvement-potential", async (c) => {
+    const body = await c.req.json().catch(() => null);
+    const parsed = z.object(checkImprovementPotentialShape).safeParse(body);
+    if (!parsed.success) return c.json({ error: "invalid_improvement_potential_request", issues: parsed.error.issues }, 400);
+    const assessment = buildStructuralImprovementAssessment(parsed.data);
+    return c.json({ improvementScore: assessment.improvementScore, band: assessment.band, findings: assessment.findings });
+  });
+
   // #6751: REST mirror of the loopover_simulate_open_pr_pressure MCP tool — deterministic, public-safe, and
   // read-only (no repo access, no GitHub writes), the same tier as the lint routes it sits with. Parses with the
   // tool's OWN exported simulateOpenPrPressureShape so the two surfaces cannot diverge on accepted input, then
diff --git a/src/mcp/server.ts b/src/mcp/server.ts
index 5310504255..4e478a078b 100644
--- a/src/mcp/server.ts
+++ b/src/mcp/server.ts
@@ -1139,7 +1139,9 @@ const evaluateEscalationOutputSchema = {
 // auth required — same choice as checkSlopRisk: a pure function over caller-supplied structured data with no
 // owner/repo/login to scope, and improvementScore carries no gate/blocker power (advisory-only; see
 // improvement.ts's header comment), so there is nothing to gate.
-const checkImprovementPotentialShape = {
+// #6748: exported so POST /v1/lint/improvement-potential parses with this EXACT shape rather than a second,
+// drifting copy — the REST mirror and this tool can never diverge on what they accept.
+export const checkImprovementPotentialShape = {
   changedFiles: z
     .array(z.object({ path: z.string().min(1).max(400), additions: z.number().int().min(0).optional(), deletions: z.number().int().min(0).optional() }))
     .max(2000)
diff --git a/test/unit/mcp-cli-improvement-potential-tool.test.ts b/test/unit/mcp-cli-improvement-potential-tool.test.ts
new file mode 100644
index 0000000000..19b12f874a
--- /dev/null
+++ b/test/unit/mcp-cli-improvement-potential-tool.test.ts
@@ -0,0 +1,88 @@
+import { Client } from "@modelcontextprotocol/sdk/client/index.js";
+import { StdioClientTransport } from "@modelcontextprotocol/sdk/client/stdio.js";
+import { mkdtempSync, rmSync } from "node:fs";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
+import { afterEach, beforeEach, describe, expect, it } from "vitest";
+import { closeFixtureServer, startFixtureServer } from "./support/mcp-cli-harness";
+
+// #6748: the CLI mirror of loopover_check_improvement_potential. It PROXIES to
+// POST /v1/lint/improvement-potential (buildStructuralImprovementAssessment lives app-side in
+// src/signals/improvement.ts, not @loopover/engine), so the route is the single source of truth for scoring.
+// The bin cannot import from src/, so its zod shape is a hand-mirror of the tool's — these tests pin that
+// mirror: valid payloads reach the route, and every bound the real schema enforces is enforced here too.
+const bin = join(process.cwd(), "packages/loopover-mcp/bin/loopover-mcp.js");
+let client: Client;
+let transport: StdioClientTransport;
+let configDir: string;
+let captured: Array<{ url: string; method: string }>;
+
+beforeEach(async () => {
+  configDir = mkdtempSync(join(tmpdir(), "loopover-improvement-"));
+  captured = [];
+  const apiUrl = await startFixtureServer({
+    onApiRequest: (request) => {
+      if (request.url?.includes("/lint/improvement-potential")) captured.push({ url: request.url ?? "", method: request.method ?? "" });
+    },
+  });
+  transport = new StdioClientTransport({
+    command: "node",
+    args: [bin, "--stdio"],
+    env: { ...process.env, LOOPOVER_CONFIG_DIR: configDir, LOOPOVER_API_URL: apiUrl, LOOPOVER_TOKEN: "session-token", LOOPOVER_API_TIMEOUT_MS: "5000" },
+  });
+  client = new Client({ name: "improvement-tool-test", version: "0.0.1" });
+  await client.connect(transport);
+});
+
+afterEach(async () => {
+  await client?.close().catch(() => undefined);
+  await closeFixtureServer();
+  if (configDir) rmSync(configDir, { recursive: true, force: true });
+});
+
+describe("loopover_check_improvement_potential stdio mirror (#6748)", () => {
+  it("registers alongside its check_slop_risk counterpart", async () => {
+    const names = new Set((await client.listTools()).tools.map((t) => t.name));
+    expect(names).toContain("loopover_check_improvement_potential");
+    expect(names).toContain("loopover_check_slop_risk");
+  });
+
+  it("proxies a full payload to POST /v1/lint/improvement-potential and returns the score", async () => {
+    const result = await client.callTool({
+      name: "loopover_check_improvement_potential",
+      arguments: {
+        changedFiles: [{ path: "src/a.ts", additions: 20, deletions: 60 }],
+        testFiles: ["test/a.test.ts"],
+        patchCoverageDeltaPercent: 4.5,
+        complexityDeltas: [{ file: "src/a.ts", line: 10, name: "handler", before: 14, after: 6, delta: -8 }],
+        duplicationDeltas: [{ file: "src/a.ts", line: 30, duplicateOfLine: 12, lines: 9 }],
+      },
+    });
+    expect(result.isError).toBeFalsy();
+    expect(captured).toHaveLength(1);
+    expect(captured[0]!.method).toBe("POST");
+    const text = JSON.stringify(result);
+    expect(text).toContain("moderate");
+    expect(text).not.toMatch(/wallet|hotkey|coldkey|trust score|reward estimate/i);
+  });
+
+  it("accepts an empty payload — every field is optional on the tool's shape", async () => {
+    const result = await client.callTool({ name: "loopover_check_improvement_potential", arguments: {} });
+    expect(result.isError).toBeFalsy();
+    expect(captured).toHaveLength(1);
+  });
+
+  it("enforces the real schema's bounds itself, before any API call", async () => {
+    for (const args of [
+      { changedFiles: [{ path: "" }] },
+      { changedFiles: [{ path: "src/a.ts", additions: -1 }] },
+      { complexityDeltas: [{ file: "src/a.ts", line: 0, name: "f", before: 1, after: 1, delta: 0 }] },
+      { duplicationDeltas: [{ file: "src/a.ts", line: 1, duplicateOfLine: 1, lines: 0 }] },
+      { patchCoverageDeltaPercent: "lots" },
+    ]) {
+      const rejected = await client.callTool({ name: "loopover_check_improvement_potential", arguments: args }).then((r) => Boolean(r.isError), () => true);
+      expect(rejected, JSON.stringify(args)).toBe(true);
+    }
+    expect(captured).toHaveLength(0);
+  });
+});
diff --git a/test/unit/mcp-tool-rename-aliases.test.ts b/test/unit/mcp-tool-rename-aliases.test.ts
index 3f7a6fa988..23d0205ab6 100644
--- a/test/unit/mcp-tool-rename-aliases.test.ts
+++ b/test/unit/mcp-tool-rename-aliases.test.ts
@@ -56,14 +56,14 @@ describe("MCP legacy alias retirement (#4777) — discovery invariants", () => {
   });
   afterEach(disconnect);
 
-  it("lists exactly 70 loopover_ tools and zero gittensory_-prefixed aliases", async () => {
+  it("lists exactly 71 loopover_ tools and zero gittensory_-prefixed aliases", async () => {
     const { tools } = await client.listTools();
     const names = tools.map((t) => t.name);
     const primary = names.filter((n) => n.startsWith("loopover_"));
     const legacy = names.filter((n) => n.startsWith("gittensory_"));
-    expect(primary.length).toBe(70);
+    expect(primary.length).toBe(71);
     expect(legacy.length).toBe(0);
-    expect(names.length).toBe(70);
+    expect(names.length).toBe(71);
   });
 
   it("no loopover_ tool's description carries a stale deprecation notice", async () => {
@@ -73,11 +73,11 @@ describe("MCP legacy alias retirement (#4777) — discovery invariants", () => {
     }
   });
 
-  it("`loopover-mcp tools --json` reports the same 70-tool count the live server registers", async () => {
+  it("`loopover-mcp tools --json` reports the same 71-tool count the live server registers", async () => {
     const { tools } = await client.listTools();
     const payload = JSON.parse(run(["tools", "--json"])) as { count: number; tools: Array<{ name: string }> };
     expect(payload.count).toBe(tools.length);
-    expect(payload.count).toBe(70);
+    expect(payload.count).toBe(71);
     expect([...payload.tools.map((t) => t.name)].sort()).toEqual([...tools.map((t) => t.name)].sort());
   });
 });
diff --git a/test/unit/routes-improvement-potential.test.ts b/test/unit/routes-improvement-potential.test.ts
new file mode 100644
index 0000000000..b7263f9dbf
--- /dev/null
+++ b/test/unit/routes-improvement-potential.test.ts
@@ -0,0 +1,76 @@
+import { describe, expect, it } from "vitest";
+import { createApp } from "../../src/api/routes";
+import { buildStructuralImprovementAssessment } from "../../src/signals/improvement";
+import { createTestEnv } from "../helpers/d1";
+
+// #6748: POST /v1/lint/improvement-potential — the REST mirror of loopover_check_improvement_potential, the one
+// deterministic lint tool whose siblings (slop-risk, issue-slop, lint-pr-text, validate-config) all already had
+// REST parity. The route parses with the tool's OWN exported shape and returns the tool handler's exact field
+// subset, so these pin the ROUTE contract; the scorer's own logic is covered by improvement's tests.
+const apiHeaders = (env: Env) => ({ authorization: `Bearer ${env.LOOPOVER_API_TOKEN}`, "content-type": "application/json" });
+const PATH = "/v1/lint/improvement-potential";
+const post = (env: Env, body: unknown) => createApp().request(PATH, { method: "POST", headers: apiHeaders(env), body: JSON.stringify(body) }, env);
+
+/** The tool's handler returns only these three fields — the mirror must not leak the rest of the assessment. */
+const subset = (input: Parameters<typeof buildStructuralImprovementAssessment>[0]) => {
+  const a = buildStructuralImprovementAssessment(input);
+  return JSON.parse(JSON.stringify({ improvementScore: a.improvementScore, band: a.band, findings: a.findings }));
+};
+
+describe("POST /v1/lint/improvement-potential (#6748)", () => {
+  it("returns the tool handler's exact field subset for a structurally-improving change", async () => {
+    const env = createTestEnv();
+    const body = {
+      changedFiles: [{ path: "src/a.ts", additions: 20, deletions: 60 }],
+      testFiles: ["test/a.test.ts"],
+      patchCoverageDeltaPercent: 4.5,
+      complexityDeltas: [{ file: "src/a.ts", line: 10, name: "handler", before: 14, after: 6, delta: -8 }],
+      duplicationDeltas: [{ file: "src/a.ts", line: 30, duplicateOfLine: 12, lines: 9 }],
+    };
+    const response = await post(env, body);
+    expect(response.status).toBe(200);
+    const payload = await response.json();
+    expect(payload).toEqual(subset(body));
+    // The mirror exposes exactly the tool's three fields — no extra assessment internals.
+    expect(Object.keys(payload as object).sort()).toEqual(["band", "findings", "improvementScore"]);
+  });
+
+  it("matches the scorer across empty, test-only, and coverage-regression inputs", async () => {
+    const env = createTestEnv();
+    for (const body of [
+      {},
+      { changedFiles: [] },
+      { changedFiles: [{ path: "src/a.ts" }] },
+      { changedFiles: [{ path: "src/a.ts" }], tests: ["ran the suite"] },
+      { changedFiles: [{ path: "src/a.ts" }], patchCoverageDeltaPercent: -12 },
+      { complexityDeltas: [{ file: "src/a.ts", line: 1, name: "f", before: 2, after: 9, delta: 7 }] },
+    ]) {
+      const response = await post(env, body);
+      expect(response.status, JSON.stringify(body)).toBe(200);
+      await expect(response.json()).resolves.toEqual(subset(body));
+    }
+  });
+
+  it("rejects input the tool's shape rejects, with 400", async () => {
+    const env = createTestEnv();
+    for (const body of [
+      { changedFiles: [{ path: "" }] },
+      { changedFiles: [{ path: "src/a.ts", additions: -1 }] },
+      { complexityDeltas: [{ file: "src/a.ts", line: 0, name: "f", before: 1, after: 1, delta: 0 }] },
+      { duplicationDeltas: [{ file: "src/a.ts", line: 1, duplicateOfLine: 1, lines: 0 }] },
+      { patchCoverageDeltaPercent: "lots" },
+    ]) {
+      const response = await post(env, body);
+      expect(response.status, JSON.stringify(body)).toBe(400);
+      await expect(response.json()).resolves.toMatchObject({ error: "invalid_improvement_potential_request" });
+    }
+    const malformed = await createApp().request(PATH, { method: "POST", headers: apiHeaders(createTestEnv()), body: "{not json" }, createTestEnv());
+    expect(malformed.status).toBe(400);
+  });
+
+  it("is public-safe: no wallet/hotkey/trust-score terms", async () => {
+    const env = createTestEnv();
+    const text = JSON.stringify(await (await post(env, { changedFiles: [{ path: "src/a.ts" }] })).json());
+    expect(text).not.toMatch(/wallet|hotkey|coldkey|trust score|reward estimate/i);
+  });
+});
diff --git a/test/unit/support/mcp-cli-harness.ts b/test/unit/support/mcp-cli-harness.ts
index 4a7e04b166..2a1b1cc085 100644
--- a/test/unit/support/mcp-cli-harness.ts
+++ b/test/unit/support/mcp-cli-harness.ts
@@ -584,6 +584,11 @@ export async function startFixtureServer(
       response.end(JSON.stringify({ repoFullName: "acme/widgets", summary: "Ranked 2 scenarios.", scenarios: [{ id: "close_stale", rank: 1 }] }));
       return;
     }
+    // #6748: the improvement-potential mirror proxies here.
+    if (request.url === "/v1/lint/improvement-potential" && request.method === "POST") {
+      response.end(JSON.stringify({ improvementScore: 62, band: "moderate", findings: [{ code: "complexity_reduced", detail: "2 functions simplified." }] }));
+      return;
+    }
     if (request.url === "/v1/repos/owner/repo/pulls/7/reviewability" && request.method === "GET") {
       response.end(
         JSON.stringify({