diff --git a/README.md b/README.md
index 647dc32..41c9125 100644
--- a/README.md
+++ b/README.md
@@ -171,6 +171,26 @@ ProfileKit cards are plain SVG. They render anywhere a platform allows external
 
 **Verified a new context?** Open a PR updating the table — the test URL is any ProfileKit endpoint, e.g. `https://profilekit.vercel.app/api/wave?text=test`.
 
+## Related projects
+
+The GitHub-profile-card space has two long-running projects ProfileKit is most often compared against. The differences are stylistic, not "better/worse" — pick the one that matches how you want to write your README.
+
+| Axis | ProfileKit | [anuraghazra/github-readme-stats](https://github.com/anuraghazra/github-readme-stats) | [lowlighter/metrics](https://github.com/lowlighter/metrics) |
+|---|---|---|---|
+| Composition unit | 28 parameter-only URL endpoints | A handful of stat endpoints | Single rendered SVG built from 30+ plugins |
+| Update model | Per-request, 30-min CDN cache (animations are SVG/CSS, not refreshes) | Per-request, CDN cache | GitHub Action runs on cron, commits the SVG into the repo |
+| Configuration | Query string + optional `theme_url=` gist for palettes | Query string + per-theme presets | YAML in `.github/workflows/` |
+| Runtime deps | Zero (Node 22 `node:test`, `node:fetch`) | Several | Action toolchain + Docker image |
+| Cards beyond GitHub stats | Hero / section / divider / now / timeline / tags / toc / typing / wave / terminal / neon / glitch / matrix / snake / equalizer / heartbeat / constellation / radar / quote / posts (devto, medium, rss) | GitHub stats, languages, pin, gists | Mostly GitHub stats; plugin set is the largest of the three |
+| MCP integration | First-class — [`@heznpc/profilekit-mcp`](https://www.npmjs.com/package/@heznpc/profilekit-mcp) lets Claude / Cursor / Codex CLI build cards as a tool call | None | None |
+| Composition into one image | `/api/stack?cards=hero,section,now,…` | Not native | The whole point of metrics is a single composed image |
+
+**When ProfileKit fits well**: you want the same card definition usable in a GitHub README *and* a dev.to bio *and* an MCP tool call, you don't want a GitHub Action committing to your repo, and "no ranking, composable presentation" sounds right for your profile.
+
+**When the alternatives fit better**: if you want one giant pre-rendered SVG with 300+ knobs in YAML, `lowlighter/metrics` is the better tool. If you only need GitHub stats blocks and want the most adopted option, `anuraghazra/github-readme-stats` is the default.
+
+(Comparison reflects the state of all three repos as of 2026-05. Open a PR if any of these projects' models change materially.)
+
 ## Endpoints
 
 | Endpoint | Description |
diff --git a/tests/endpoint-headers.test.js b/tests/endpoint-headers.test.js
new file mode 100644
index 0000000..382d951
--- /dev/null
+++ b/tests/endpoint-headers.test.js
@@ -0,0 +1,111 @@
+const test = require("node:test");
+const assert = require("node:assert/strict");
+
+// Regression test for response headers ProfileKit relies on for correct
+// rendering through GitHub's Camo proxy and other image proxies.
+//
+// Why this exists: market-pulse 2026-05 surfaced that GitHub's Camo cache
+// behavior depends on a stable Content-Type and Cache-Control header. A
+// silent change (someone "tidies up" an endpoint and drops `image/svg+xml`,
+// or replaces `cacheHeaders()` with `no-store`) would result in Camo
+// re-fetching every request and animations stuttering for embedders. None
+// of the existing tests check the wire-level response headers.
+
+function makeMockReq(query = {}) {
+  // Vercel-style req: url + parsed query. parseSearchParams in options.js
+  // only reads `req.url`, so the query object isn't strictly needed, but we
+  // include it for handlers that hit `req.query` directly.
+  const qs = new URLSearchParams(query).toString();
+  return {
+    url: qs ? `/api/_test?${qs}` : "/api/_test",
+    query,
+    method: "GET",
+    headers: { host: "profilekit.local" },
+  };
+}
+
+function makeMockRes() {
+  const headers = {};
+  let body;
+  let statusCode = 200;
+  return {
+    setHeader(name, value) {
+      headers[name] = value;
+    },
+    getHeader(name) {
+      return headers[name];
+    },
+    status(code) {
+      statusCode = code;
+      return this;
+    },
+    send(payload) {
+      body = payload;
+      return this;
+    },
+    _inspect() {
+      return { headers, body, statusCode };
+    },
+  };
+}
+
+test("/api/divider emits Content-Type: image/svg+xml + cached", async () => {
+  // SVG endpoints must declare image/svg+xml so Camo accepts and caches
+  // them. A regression to text/html or application/octet-stream causes
+  // GitHub READMEs to render a broken-image icon.
+  const handler = require("../src/endpoints/divider");
+  const req = makeMockReq({ style: "line", width: "400" });
+  const res = makeMockRes();
+  await handler(req, res);
+  const { headers, body } = res._inspect();
+  assert.equal(headers["Content-Type"], "image/svg+xml", "Content-Type must be image/svg+xml");
+  assert.match(
+    headers["Cache-Control"] || "",
+    /max-age=\d+/,
+    "Cache-Control must include a max-age so Camo caches and re-fetches deterministically"
+  );
+  assert.ok(typeof body === "string" && body.startsWith("<svg"), "body must be SVG markup");
+});
+
+test("/api/health emits no-store cache so probes always observe current state", async () => {
+  // Probes (Pingdom, statuspage) and uptime monitors must observe the
+  // current pool state, not a cached snapshot. A regression to a long
+  // max-age would mask token-pool drainage incidents.
+  const handler = require("../src/endpoints/health");
+  const res = makeMockRes();
+  await handler(makeMockReq(), res);
+  const { headers, body } = res._inspect();
+  assert.match(headers["Content-Type"], /application\/json/, "/api/health must return JSON");
+  assert.match(
+    headers["Cache-Control"] || "",
+    /no-store/,
+    "/api/health must never be cached"
+  );
+  const parsed = JSON.parse(body);
+  assert.equal(parsed.ok, true);
+  assert.ok(parsed.allowlists, "/api/health must surface allowlists for visibility");
+});
+
+test("/api/catalog emits JSON + cached", async () => {
+  // Discovery endpoint consumed by @heznpc/profilekit-mcp. A regression
+  // to text/plain would break the wrapper's JSON.parse, and missing
+  // Cache-Control would hammer the function on every MCP discover call.
+  const handler = require("../src/endpoints/catalog");
+  const res = makeMockRes();
+  await handler(makeMockReq(), res);
+  const { headers, body } = res._inspect();
+  assert.match(headers["Content-Type"], /application\/json/, "/api/catalog must return JSON");
+  assert.match(
+    headers["Cache-Control"] || "",
+    /max-age=\d+/,
+    "/api/catalog must be cached so MCP discovery doesn't re-execute the handler per request"
+  );
+  const parsed = JSON.parse(body);
+  assert.ok(parsed.cards && parsed.themes, "catalog must declare cards + themes");
+  // Cross-check with the market-pulse-driven contract: theme_url must be
+  // advertised on every card endpoint, not just stats/stack.
+  assert.ok(
+    parsed.cards.hero.common_params.includes("theme_url"),
+    "hero must list theme_url in common_params (matches README claim)"
+  );
+});