diff --git a/src/routes/credentials.js b/src/routes/credentials.js
index 8444fb0..1693275 100644
--- a/src/routes/credentials.js
+++ b/src/routes/credentials.js
@@ -6,6 +6,42 @@ import {Router} from 'express';
 
 /** @typedef {import('../types.js').VerifiableCredential} VerifiableCredential */
 
+/**
+ * Validates required credential fields per the VC-API issuer test suite.
+ * Returns an error message string, or null if valid.
+ *
+ * @param {Record<string, any>} credential
+ * @returns {string | null}
+ */
+function validateCredentialFields(credential) {
+  if(!Array.isArray(credential['@context'])) {
+    return 'credential "@context" must be an array.';
+  }
+  if(!credential['@context'].every(item => typeof item === 'string')) {
+    return 'credential "@context" items must be strings.';
+  }
+  if(!Array.isArray(credential.type)) {
+    return 'credential "type" must be an array.';
+  }
+  if(!credential.type.every(item => typeof item === 'string')) {
+    return 'credential "type" items must be strings.';
+  }
+  if(credential.issuer === undefined || credential.issuer === null) {
+    return 'credential must have property "issuer".';
+  }
+  if(typeof credential.issuer !== 'string' &&
+    (typeof credential.issuer !== 'object' ||
+      Array.isArray(credential.issuer))) {
+    return 'credential "issuer" must be a string or an object.';
+  }
+  if(!credential.credentialSubject ||
+    typeof credential.credentialSubject !== 'object' ||
+    Array.isArray(credential.credentialSubject)) {
+    return 'credential "credentialSubject" must be an object.';
+  }
+  return null;
+}
+
 /**
  * @param {import('../store/index.js').createStore extends
  *   (...args: any[]) => infer R ? R : never} store
@@ -25,6 +61,13 @@ export function credentialsRouter(store) {
       );
     }
 
+    const invalid = validateCredentialFields(credential);
+    if(invalid) {
+      return res.status(400).json(
+        problemDetails('invalid-input', 'Invalid Input', 400, invalid)
+      );
+    }
+
     const credentialId =
       options.credentialId ?? credential.id ?? randomUUID();
     const mandatoryPointers = options.mandatoryPointers ?? [];
diff --git a/test/integration/credentials.test.js b/test/integration/credentials.test.js
index 211eb5a..70a62dc 100644
--- a/test/integration/credentials.test.js
+++ b/test/integration/credentials.test.js
@@ -29,6 +29,95 @@ describe('POST /credentials/issue', () => {
     assert.ok(res.body.type.includes('invalid-input'));
   });
 
+  // vc-api-issuer-test-suite conformance checks
+  /** @type {Array<{label: string, mutate: (c: Record<string, any>) => void}>} */
+  const invalidInputCases = [
+    {
+      label: 'missing @context',
+      mutate: c => {
+        delete c['@context'];
+      }
+    },
+    {
+      label: '@context not an array',
+      mutate: c => {
+        c['@context'] = 4;
+      }
+    },
+    {
+      label: '@context item not a string',
+      mutate: c => {
+        c['@context'] = [{foo: true}];
+      }
+    },
+    {
+      label: 'missing type',
+      mutate: c => {
+        delete c.type;
+      }
+    },
+    {
+      label: 'type not an array',
+      mutate: c => {
+        c.type = 4;
+      }
+    },
+    {
+      label: 'type item not a string',
+      mutate: c => {
+        c.type = [null];
+      }
+    },
+    {
+      label: 'missing issuer',
+      mutate: c => {
+        delete c.issuer;
+      }
+    },
+    {
+      label: 'issuer invalid type',
+      mutate: c => {
+        c.issuer = 4;
+      }
+    },
+    {
+      label: 'missing credentialSubject',
+      mutate: c => {
+        delete c.credentialSubject;
+      }
+    },
+    {
+      label: 'credentialSubject not an object',
+      mutate: c => {
+        c.credentialSubject = 'did:example:1234';
+      }
+    }
+  ];
+
+  for(const {label, mutate} of invalidInputCases) {
+    it(`should return 400 when credential has ${label}`, async () => {
+      const credential = unsignedCredential();
+      mutate(credential);
+      const res = await request(app)
+        .post('/credentials/issue')
+        .send({credential});
+      assert.equal(res.status, 400, `Expected 400 for: ${label}`);
+      assert.ok(res.body.type.includes('invalid-input'));
+    });
+  }
+
+  it('should return 201 when credential has expirationDate', async () => {
+    const cred = unsignedCredential();
+    const credential = /** @type {Record<string, any>} */ (cred);
+    credential.expirationDate =
+      new Date(Date.now() + 365 * 24 * 60 * 60 * 1000).toISOString()
+        .replace(/\.\d+Z$/, 'Z');
+    const res = await request(app)
+      .post('/credentials/issue')
+      .send({credential});
+    assert.equal(res.status, 201);
+  });
+
   it('should store the credential by credentialId option', async () => {
     const credentialId = 'test-cred-123';
     await request(app)