diff --git a/src/utilities/__tests__/buildClientSchema-test.js b/src/utilities/__tests__/buildClientSchema-test.js
index b474fc423a..6ad7618fa7 100644
--- a/src/utilities/__tests__/buildClientSchema-test.js
+++ b/src/utilities/__tests__/buildClientSchema-test.js
@@ -29,10 +29,10 @@ import { introspectionFromSchema } from '../introspectionFromSchema';
 /**
  * This function does a full cycle of going from a string with the contents of
  * the SDL, build in-memory GraphQLSchema from it, produce a client-side
- * representation of the schema by using "buildClientSchema"and then finally
- * printing that that schema into the SDL
+ * representation of the schema by using "buildClientSchema" and then
+ * returns that schema printed as SDL.
  */
-function cycleIntrospection(sdlString) {
+function cycleIntrospection(sdlString: string): string {
   const serverSchema = buildSchema(sdlString);
   const initialIntrospection = introspectionFromSchema(serverSchema);
   const clientSchema = buildClientSchema(initialIntrospection);
@@ -53,7 +53,7 @@ describe('Type System: build schema from introspection', () => {
         query: Simple
       }
 
-      """This is simple type"""
+      """This is a simple type"""
       type Simple {
         """This is a string field"""
         string: String
@@ -143,7 +143,7 @@ describe('Type System: build schema from introspection', () => {
     expect(clientSchema.getType('CustomScalar')).not.to.equal(customScalar);
   });
 
-  it('include standard type only if it is used', () => {
+  it('includes standard types only if they are used', () => {
     const schema = buildSchema(`
       type Query {
         foo: String
@@ -604,12 +604,12 @@ describe('Type System: build schema from introspection', () => {
     it('throws when introspection is missing __schema property', () => {
       // $DisableFlowOnNegativeTest
       expect(() => buildClientSchema(null)).to.throw(
-        'Invalid or incomplete introspection result. Ensure that you are passing "data" property of introspection response and no "errors" was returned alongside: null',
+        'Invalid or incomplete introspection result. Ensure that you are passing "data" property of introspection response and no "errors" was returned alongside: null.',
       );
 
       // $DisableFlowOnNegativeTest
       expect(() => buildClientSchema({})).to.throw(
-        'Invalid or incomplete introspection result. Ensure that you are passing "data" property of introspection response and no "errors" was returned alongside: {}',
+        'Invalid or incomplete introspection result. Ensure that you are passing "data" property of introspection response and no "errors" was returned alongside: {}.',
       );
     });
 
@@ -653,7 +653,7 @@ describe('Type System: build schema from introspection', () => {
       delete introspection.__schema.queryType.name;
 
       expect(() => buildClientSchema(introspection)).to.throw(
-        'Unknown type reference: {}',
+        'Unknown type reference: {}.',
       );
     });
 
@@ -669,7 +669,7 @@ describe('Type System: build schema from introspection', () => {
       delete queryTypeIntrospection.kind;
 
       expect(() => buildClientSchema(introspection)).to.throw(
-        'Invalid or incomplete introspection result. Ensure that a full introspection query is used in order to build a client schema',
+        /Invalid or incomplete introspection result. Ensure that a full introspection query is used in order to build a client schema: { name: "Query", .* }\./,
       );
     });
 
@@ -685,7 +685,7 @@ describe('Type System: build schema from introspection', () => {
       delete queryTypeIntrospection.interfaces;
 
       expect(() => buildClientSchema(introspection)).to.throw(
-        'Introspection result missing interfaces: { kind: "OBJECT", name: "Query",',
+        /Introspection result missing interfaces: { kind: "OBJECT", name: "Query", .* }\./,
       );
     });
 
@@ -715,7 +715,7 @@ describe('Type System: build schema from introspection', () => {
       delete queryTypeIntrospection.fields;
 
       expect(() => buildClientSchema(introspection)).to.throw(
-        'Introspection result missing fields: { kind: "OBJECT", name: "Query",',
+        /Introspection result missing fields: { kind: "OBJECT", name: "Query", .* }\./,
       );
     });
 
@@ -731,7 +731,7 @@ describe('Type System: build schema from introspection', () => {
       delete queryTypeIntrospection.fields[0].args;
 
       expect(() => buildClientSchema(introspection)).to.throw(
-        'Introspection result missing field args: { name: "foo",',
+        /Introspection result missing field args: { name: "foo", .* }\./,
       );
     });
 
@@ -783,7 +783,7 @@ describe('Type System: build schema from introspection', () => {
       delete someUnionIntrospection.possibleTypes;
 
       expect(() => buildClientSchema(introspection)).to.throw(
-        'Introspection result missing possibleTypes: { kind: "UNION", name: "SomeUnion",',
+        /Introspection result missing possibleTypes: { kind: "UNION", name: "SomeUnion",.* }\./,
       );
     });
 
@@ -799,7 +799,7 @@ describe('Type System: build schema from introspection', () => {
       delete someEnumIntrospection.enumValues;
 
       expect(() => buildClientSchema(introspection)).to.throw(
-        'Introspection result missing enumValues: { kind: "ENUM", name: "SomeEnum",',
+        /Introspection result missing enumValues: { kind: "ENUM", name: "SomeEnum", .* }\./,
       );
     });
 
@@ -815,7 +815,7 @@ describe('Type System: build schema from introspection', () => {
       delete someInputObjectIntrospection.inputFields;
 
       expect(() => buildClientSchema(introspection)).to.throw(
-        'Introspection result missing inputFields: { kind: "INPUT_OBJECT", name: "SomeInputObject",',
+        /Introspection result missing inputFields: { kind: "INPUT_OBJECT", name: "SomeInputObject", .* }\./,
       );
     });
 
@@ -832,7 +832,7 @@ describe('Type System: build schema from introspection', () => {
       delete someDirectiveIntrospection.locations;
 
       expect(() => buildClientSchema(introspection)).to.throw(
-        'Introspection result missing directive locations: { name: "SomeDirective",',
+        /Introspection result missing directive locations: { name: "SomeDirective", .* }\./,
       );
     });
 
@@ -849,7 +849,7 @@ describe('Type System: build schema from introspection', () => {
       delete someDirectiveIntrospection.args;
 
       expect(() => buildClientSchema(introspection)).to.throw(
-        'Introspection result missing directive args: { name: "SomeDirective",',
+        /Introspection result missing directive args: { name: "SomeDirective", .* }\./,
       );
     });
   });
diff --git a/src/utilities/buildClientSchema.js b/src/utilities/buildClientSchema.js
index bedb9118d0..45c96b2bc1 100644
--- a/src/utilities/buildClientSchema.js
+++ b/src/utilities/buildClientSchema.js
@@ -74,8 +74,9 @@ export function buildClientSchema(
 ): GraphQLSchema {
   devAssert(
     isObjectLike(introspection) && isObjectLike(introspection.__schema),
-    'Invalid or incomplete introspection result. Ensure that you are passing "data" property of introspection response and no "errors" was returned alongside: ' +
-      inspect(introspection),
+    `Invalid or incomplete introspection result. Ensure that you are passing "data" property of introspection response and no "errors" was returned alongside: ${inspect(
+      introspection,
+    )}.`,
   );
 
   // Get the schema from the introspection result.
@@ -88,6 +89,7 @@ export function buildClientSchema(
     typeIntrospection => buildType(typeIntrospection),
   );
 
+  // Include standard types only if they are used.
   for (const stdType of [...specifiedScalarTypes, ...introspectionTypes]) {
     if (typeMap[stdType.name]) {
       typeMap[stdType.name] = stdType;
@@ -142,7 +144,7 @@ export function buildClientSchema(
       return GraphQLNonNull(assertNullableType(nullableType));
     }
     if (!typeRef.name) {
-      throw new Error('Unknown type reference: ' + inspect(typeRef));
+      throw new Error(`Unknown type reference: ${inspect(typeRef)}.`);
     }
     return getNamedType(typeRef.name);
   }
@@ -163,10 +165,9 @@ export function buildClientSchema(
     if (isInputType(type)) {
       return type;
     }
+    const typeStr = inspect(type);
     throw new Error(
-      'Introspection must provide input type for arguments, but received: ' +
-        inspect(type) +
-        '.',
+      `Introspection must provide input type for arguments, but received: ${typeStr}.`,
     );
   }
 
@@ -177,10 +178,9 @@ export function buildClientSchema(
     if (isOutputType(type)) {
       return type;
     }
+    const typeStr = inspect(type);
     throw new Error(
-      'Introspection must provide output type for fields, but received: ' +
-        inspect(type) +
-        '.',
+      `Introspection must provide output type for fields, but received: ${typeStr}.`,
     );
   }
 
@@ -217,9 +217,9 @@ export function buildClientSchema(
           return buildInputObjectDef(type);
       }
     }
+    const typeStr = inspect(type);
     throw new Error(
-      'Invalid or incomplete introspection result. Ensure that a full introspection query is used in order to build a client schema:' +
-        inspect(type),
+      `Invalid or incomplete introspection result. Ensure that a full introspection query is used in order to build a client schema: ${typeStr}.`,
     );
   }
 
@@ -247,9 +247,9 @@ export function buildClientSchema(
     }
 
     if (!implementingIntrospection.interfaces) {
+      const implementingIntrospectionStr = inspect(implementingIntrospection);
       throw new Error(
-        'Introspection result missing interfaces: ' +
-          inspect(implementingIntrospection),
+        `Introspection result missing interfaces: ${implementingIntrospectionStr}.`,
       );
     }
 
@@ -282,9 +282,9 @@ export function buildClientSchema(
     unionIntrospection: IntrospectionUnionType,
   ): GraphQLUnionType {
     if (!unionIntrospection.possibleTypes) {
+      const unionIntrospectionStr = inspect(unionIntrospection);
       throw new Error(
-        'Introspection result missing possibleTypes: ' +
-          inspect(unionIntrospection),
+        `Introspection result missing possibleTypes: ${unionIntrospectionStr}.`,
       );
     }
     return new GraphQLUnionType({
@@ -298,9 +298,9 @@ export function buildClientSchema(
     enumIntrospection: IntrospectionEnumType,
   ): GraphQLEnumType {
     if (!enumIntrospection.enumValues) {
+      const enumIntrospectionStr = inspect(enumIntrospection);
       throw new Error(
-        'Introspection result missing enumValues: ' +
-          inspect(enumIntrospection),
+        `Introspection result missing enumValues: ${enumIntrospectionStr}.`,
       );
     }
     return new GraphQLEnumType({
@@ -321,9 +321,9 @@ export function buildClientSchema(
     inputObjectIntrospection: IntrospectionInputObjectType,
   ): GraphQLInputObjectType {
     if (!inputObjectIntrospection.inputFields) {
+      const inputObjectIntrospectionStr = inspect(inputObjectIntrospection);
       throw new Error(
-        'Introspection result missing inputFields: ' +
-          inspect(inputObjectIntrospection),
+        `Introspection result missing inputFields: ${inputObjectIntrospectionStr}.`,
       );
     }
     return new GraphQLInputObjectType({
@@ -336,7 +336,7 @@ export function buildClientSchema(
   function buildFieldDefMap(typeIntrospection) {
     if (!typeIntrospection.fields) {
       throw new Error(
-        'Introspection result missing fields: ' + inspect(typeIntrospection),
+        `Introspection result missing fields: ${inspect(typeIntrospection)}.`,
       );
     }
     return keyValMap(
@@ -344,9 +344,9 @@ export function buildClientSchema(
       fieldIntrospection => fieldIntrospection.name,
       fieldIntrospection => {
         if (!fieldIntrospection.args) {
+          const fieldIntrospectionStr = inspect(fieldIntrospection);
           throw new Error(
-            'Introspection result missing field args: ' +
-              inspect(fieldIntrospection),
+            `Introspection result missing field args: ${fieldIntrospectionStr}.`,
           );
         }
         return {
@@ -382,15 +382,15 @@ export function buildClientSchema(
 
   function buildDirective(directiveIntrospection) {
     if (!directiveIntrospection.args) {
+      const directiveIntrospectionStr = inspect(directiveIntrospection);
       throw new Error(
-        'Introspection result missing directive args: ' +
-          inspect(directiveIntrospection),
+        `Introspection result missing directive args: ${directiveIntrospectionStr}.`,
       );
     }
     if (!directiveIntrospection.locations) {
+      const directiveIntrospectionStr = inspect(directiveIntrospection);
       throw new Error(
-        'Introspection result missing directive locations: ' +
-          inspect(directiveIntrospection),
+        `Introspection result missing directive locations: ${directiveIntrospectionStr}.`,
       );
     }
     return new GraphQLDirective({