diff --git a/src/mcp/server.ts b/src/mcp/server.ts
index 7829e7034c..eeaa1c39e8 100644
--- a/src/mcp/server.ts
+++ b/src/mcp/server.ts
@@ -252,6 +252,104 @@ const variantsShape = {
   variants: z.array(z.object(scorePreviewShape)).min(1).max(10),
 };
 
+// ── MCP tool output schemas ────────────────────────────────────────────────
+// Structured-output metadata for machine-readable tools so modern MCP clients
+// can discover and validate Gittensory responses. Schemas declare documented
+// top-level fields; complex/nullable/variant fields use a permissive type so
+// validation never rejects a real response (the SDK strips unknown keys). All
+// fields are optional because several tools return either a result payload or a
+// `{ status: "not_found" | ... }` / refresh envelope.
+const repoContextOutputSchema = {
+  repoFullName: z.string().optional(),
+  repo: z.unknown().optional(),
+  lane: z.unknown().optional(),
+  queueHealth: z.unknown().optional(),
+  collisions: z.unknown().optional(),
+  configQuality: z.unknown().optional(),
+  dataQuality: z.unknown().optional(),
+};
+
+const freshnessResponseOutputSchema = {
+  status: z.string().optional(),
+  repoFullName: z.string().optional(),
+  source: z.string().optional(),
+  freshness: z.string().optional(),
+  generatedAt: z.string().optional(),
+  report: z.unknown().optional(),
+};
+
+const contributorProfileOutputSchema = {
+  login: z.string().optional(),
+  github: z.unknown().optional(),
+  source: z.unknown().optional(),
+  repoStats: z.unknown().optional(),
+  trustSignals: z.unknown().optional(),
+};
+
+const decisionPackOutputSchema = {
+  status: z.string().optional(),
+  login: z.string().optional(),
+  source: z.string().optional(),
+  freshness: z.string().optional(),
+  generatedAt: z.string().optional(),
+  rebuildEnqueued: z.boolean().optional(),
+  summary: z.string().optional(),
+  repoDecisions: z.unknown().optional(),
+  topActions: z.unknown().optional(),
+};
+
+const openPrMonitorOutputSchema = {
+  login: z.string().optional(),
+  generatedAt: z.string().optional(),
+  openPrCount: z.number().optional(),
+  registeredRepoCount: z.number().optional(),
+  cleanupFirst: z.boolean().optional(),
+  summary: z.string().optional(),
+  guidance: z.unknown().optional(),
+  pendingScenarios: z.unknown().optional(),
+  pullRequests: z.unknown().optional(),
+};
+
+const explainRepoDecisionOutputSchema = {
+  status: z.string().optional(),
+  login: z.string().optional(),
+  repoFullName: z.string().optional(),
+  generatedAt: z.string().optional(),
+  source: z.string().optional(),
+  freshness: z.string().optional(),
+  rebuildEnqueued: z.boolean().optional(),
+  decision: z.unknown().optional(),
+  dataQuality: z.unknown().optional(),
+};
+
+const registryChangesOutputSchema = {
+  generatedAt: z.string().optional(),
+  previous: z.unknown().optional(),
+  current: z.unknown().optional(),
+  added: z.unknown().optional(),
+  removed: z.unknown().optional(),
+  changed: z.unknown().optional(),
+  warnings: z.unknown().optional(),
+};
+
+const upstreamDriftOutputSchema = {
+  generatedAt: z.string().optional(),
+  status: z.string().optional(),
+  latestCommitSha: z.string().nullable().optional(),
+  latestRulesetId: z.string().nullable().optional(),
+  highestSeverity: z.string().nullable().optional(),
+  affectedAreas: z.unknown().optional(),
+  openReportCount: z.number().optional(),
+  reports: z.unknown().optional(),
+};
+
+const localStatusOutputSchema = {
+  apiAvailable: z.boolean().optional(),
+  sourceUploadDefault: z.boolean().optional(),
+  supportedEndpoint: z.string().optional(),
+  supportedTools: z.unknown().optional(),
+};
+
 export async function handleMcpRequest(c: AppContext): Promise<Response> {
   if (c.req.method === "OPTIONS") return new Response(null, { status: 204 });
   const identity = await authenticateMcpRequest(c);
@@ -324,6 +422,7 @@ export class GittensoryMcp {
       {
         description: "Return Gittensory repo context: registration, lane, queue health, collisions, and config quality.",
         inputSchema: ownerRepoShape,
+        outputSchema: repoContextOutputSchema,
       },
       async (input) => this.toolResult(await this.getRepoContext(input)),
     );
@@ -333,6 +432,7 @@ export class GittensoryMcp {
       {
         description: "Return the cached or freshly-computed maintainer burden forecast for a repo, including projected review load, queue growth risk, stale PR signals, and a freshness marker.",
         inputSchema: ownerRepoShape,
+        outputSchema: freshnessResponseOutputSchema,
       },
       async (input) => this.toolResult(await this.getBurdenForecast(input)),
     );
@@ -342,6 +442,7 @@ export class GittensoryMcp {
       {
         description: "Return cached or freshly-computed per-repo accepted/rejected PR outcome patterns: what maintainers actually merge or close, separated from maintainer-lane activity, with a freshness marker and explicit evidence-completeness.",
         inputSchema: ownerRepoShape,
+        outputSchema: freshnessResponseOutputSchema,
       },
       async (input) => this.toolResult(await this.getRepoOutcomePatterns(input)),
     );
@@ -351,6 +452,7 @@ export class GittensoryMcp {
       {
         description: "Return an evidence-backed Gittensory contributor profile for a GitHub login.",
         inputSchema: loginShape,
+        outputSchema: contributorProfileOutputSchema,
       },
       async (input) => this.toolResult(await this.getContributorProfile(input.login)),
     );
@@ -360,6 +462,7 @@ export class GittensoryMcp {
       {
         description: "Return the canonical private contributor decision pack for a GitHub login.",
         inputSchema: loginShape,
+        outputSchema: decisionPackOutputSchema,
       },
       async (input) => this.toolResult(await this.getDecisionPack(input.login)),
     );
@@ -370,6 +473,7 @@ export class GittensoryMcp {
         description:
           "Inspect a contributor's open PRs on registered repos, classify queue state, and return public-safe next-step packets from cached metadata.",
         inputSchema: loginShape,
+        outputSchema: openPrMonitorOutputSchema,
       },
       async (input) => this.toolResult(await this.monitorOpenPullRequests(input.login)),
     );
@@ -379,6 +483,7 @@ export class GittensoryMcp {
       {
         description: "Return the contributor/repo decision from the canonical decision pack.",
         inputSchema: loginRepoShape,
+        outputSchema: explainRepoDecisionOutputSchema,
       },
       async (input) => this.toolResult(await this.explainRepoDecision(input)),
     );
@@ -406,6 +511,7 @@ export class GittensoryMcp {
       {
         description: "Return the diff between the latest cached Gittensor registry snapshots.",
         inputSchema: {},
+        outputSchema: registryChangesOutputSchema,
       },
       async () => this.toolResult(await this.getRegistryChanges()),
     );
@@ -415,6 +521,7 @@ export class GittensoryMcp {
       {
         description: "Return private upstream Gittensor ruleset drift status, including stale/drift warnings for MCP planning.",
         inputSchema: {},
+        outputSchema: upstreamDriftOutputSchema,
       },
       async () => this.toolResult(await this.getUpstreamDrift()),
     );
@@ -424,6 +531,7 @@ export class GittensoryMcp {
       {
         description: "Return the cached or freshly-computed issue-quality report for a repo, ranking which open issues are actionable, need proof, are stale/duplicate-prone, or already solved.",
         inputSchema: ownerRepoShape,
+        outputSchema: freshnessResponseOutputSchema,
       },
       async (input) => this.toolResult(await this.getIssueQuality(input)),
     );
@@ -469,6 +577,7 @@ export class GittensoryMcp {
       {
         description: "Return Gittensory local-MCP contract status and privacy defaults.",
         inputSchema: {},
+        outputSchema: localStatusOutputSchema,
       },
       async () =>
         this.toolResult({
diff --git a/test/unit/mcp-output-schemas.test.ts b/test/unit/mcp-output-schemas.test.ts
new file mode 100644
index 0000000000..d1473ef996
--- /dev/null
+++ b/test/unit/mcp-output-schemas.test.ts
@@ -0,0 +1,141 @@
+import { Client } from "@modelcontextprotocol/sdk/client/index.js";
+import { InMemoryTransport } from "@modelcontextprotocol/sdk/inMemory.js";
+import { describe, expect, it } from "vitest";
+import { GittensoryMcp } from "../../src/mcp/server";
+import { createTestEnv } from "../helpers/d1";
+
+// Tools that ship an MCP-native output schema so modern clients can validate/render responses.
+const TOOLS_WITH_OUTPUT_SCHEMA = [
+  "gittensory_get_repo_context",
+  "gittensory_get_burden_forecast",
+  "gittensory_get_repo_outcome_patterns",
+  "gittensory_get_contributor_profile",
+  "gittensory_get_decision_pack",
+  "gittensory_monitor_open_prs",
+  "gittensory_explain_repo_decision",
+  "gittensory_get_issue_quality",
+  "gittensory_get_registry_changes",
+  "gittensory_get_upstream_drift",
+  "gittensory_local_status",
+];
+
+async function connectTestClient() {
+  const mcpServer = new GittensoryMcp(createTestEnv()).createServer();
+  const [clientTransport, serverTransport] = InMemoryTransport.createLinkedPair();
+  await mcpServer.connect(serverTransport);
+  const client = new Client({ name: "gittensory-output-schema-test", version: "0.1.0" }, { capabilities: {} });
+  await client.connect(clientTransport);
+  return { client, mcpServer };
+}
+
+// ── Output schema discovery ────────────────────────────────────────────────────
+
+describe("MCP output schema discovery", () => {
+  it("exposes an outputSchema for every covered tool in tools/list", async () => {
+    const { client } = await connectTestClient();
+    const { tools } = await client.listTools();
+    const byName = new Map(tools.map((t) => [t.name, t]));
+
+    for (const name of TOOLS_WITH_OUTPUT_SCHEMA) {
+      const tool = byName.get(name);
+      expect(tool, `expected tool "${name}" to be registered`).toBeDefined();
+      expect(tool?.outputSchema, `expected tool "${name}" to expose an outputSchema`).toBeDefined();
+      expect(tool?.outputSchema?.type).toBe("object");
+    }
+  });
+
+  it("output schemas declare documented top-level properties", async () => {
+    const { client } = await connectTestClient();
+    const { tools } = await client.listTools();
+    const byName = new Map(tools.map((t) => [t.name, t]));
+
+    const repoContext = byName.get("gittensory_get_repo_context");
+    const repoContextProps = Object.keys((repoContext?.outputSchema?.properties ?? {}) as Record<string, unknown>);
+    expect(repoContextProps).toEqual(expect.arrayContaining(["repoFullName", "lane", "queueHealth", "configQuality"]));
+
+    const upstream = byName.get("gittensory_get_upstream_drift");
+    const upstreamProps = Object.keys((upstream?.outputSchema?.properties ?? {}) as Record<string, unknown>);
+    expect(upstreamProps).toEqual(expect.arrayContaining(["status", "highestSeverity"]));
+
+    const localStatus = byName.get("gittensory_local_status");
+    const localStatusProps = Object.keys((localStatus?.outputSchema?.properties ?? {}) as Record<string, unknown>);
+    expect(localStatusProps).toEqual(expect.arrayContaining(["apiAvailable", "supportedEndpoint"]));
+  });
+
+  it("preserves the full tool inventory while adding output schemas", async () => {
+    const { client } = await connectTestClient();
+    const { tools } = await client.listTools();
+    const names = new Set(tools.map((t) => t.name));
+
+    // A representative slice of tools without output schemas remains intact.
+    expect(names.has("gittensory_preflight_pr")).toBe(true);
+    expect(names.has("gittensory_agent_plan_next_work")).toBe(true);
+    expect(names.has("gittensory_compare_pr_variants")).toBe(true);
+  });
+});
+
+// ── Structured content validates against the declared schema ─────────────────────
+
+describe("MCP tool calls return schema-valid structured content", () => {
+  it("gittensory_local_status returns validated structured content", async () => {
+    const { client } = await connectTestClient();
+    const result = await client.callTool({ name: "gittensory_local_status", arguments: {} });
+    expect(result.isError).toBeFalsy();
+    expect(result.structuredContent).toBeDefined();
+    const data = result.structuredContent as Record<string, unknown>;
+    expect(data.apiAvailable).toBe(true);
+    expect(data.supportedEndpoint).toBe("/v1/local/branch-analysis");
+  });
+
+  it("gittensory_get_upstream_drift returns validated structured content", async () => {
+    const { client } = await connectTestClient();
+    const result = await client.callTool({ name: "gittensory_get_upstream_drift", arguments: {} });
+    expect(result.isError).toBeFalsy();
+    const data = result.structuredContent as Record<string, unknown>;
+    expect(["current", "drift_detected", "stale", "unavailable"]).toContain(data.status);
+  });
+
+  it("gittensory_get_registry_changes returns validated structured content", async () => {
+    const { client } = await connectTestClient();
+    const result = await client.callTool({ name: "gittensory_get_registry_changes", arguments: {} });
+    expect(result.isError).toBeFalsy();
+    expect(result.structuredContent).toBeDefined();
+  });
+
+  it("gittensory_get_repo_context returns validated structured content", async () => {
+    const { client } = await connectTestClient();
+    const result = await client.callTool({ name: "gittensory_get_repo_context", arguments: { owner: "octo", repo: "demo" } });
+    expect(result.isError).toBeFalsy();
+    const data = result.structuredContent as Record<string, unknown>;
+    expect(data.repoFullName).toBe("octo/demo");
+  });
+});
+
+// ── Public/private safety ─────────────────────────────────────────────────────
+
+describe("MCP output schemas do not declare private financial fields", () => {
+  it("no output schema exposes wallet/hotkey/coldkey/financial property names", async () => {
+    const { client } = await connectTestClient();
+    const { tools } = await client.listTools();
+
+    for (const tool of tools) {
+      if (!tool.outputSchema) continue;
+      const serialized = JSON.stringify(tool.outputSchema);
+      expect(serialized, `tool "${tool.name}" output schema must not declare private fields`).not.toMatch(
+        /hotkey|coldkey|wallet|mnemonic|alphaPerDay|taoPerDay|usdPerDay|rawTrust|privateReviewability/i,
+      );
+    }
+  });
+
+  it("structured content from public-safe tools never includes redacted financial keys", async () => {
+    const { client } = await connectTestClient();
+
+    for (const name of ["gittensory_local_status", "gittensory_get_upstream_drift", "gittensory_get_registry_changes"]) {
+      const result = await client.callTool({ name, arguments: {} });
+      const serialized = JSON.stringify(result.structuredContent ?? {});
+      expect(serialized, `tool "${name}" structured content must not leak financial fields`).not.toMatch(
+        /hotkey|coldkey|wallet|mnemonic|alphaPerDay|taoPerDay|usdPerDay/i,
+      );
+    }
+  });
+});