fix(mcp): relax Boolean literals without narrowing valid inputs

Normalize only advertised schema positions while keeping canonical validation. Preserve branch guidance and relax nonmonotone constraints as a unit. Verify full/compact catalogs and canonical examples after SDK conversion.

Refs #4025, #4087

Co-authored-by: HarsH <harshasalkar7@gmail.com>

docs/mcp-contracts.md

@@ -694,6 +694,20 @@ after SDK conversion and check advertised validation and actual calls.
 Individual model APIs can impose additional nesting limits; complete producer
 captures can exceed ten structural levels.
 
+Boolean literal constraints in input schemas are relaxed only in this
+advertisement. For example, a boolean `const` is presented as `type: boolean`;
+an affected `not` is omitted, conditional predicates and their branches are
+omitted together, pure boolean-literal `oneOf` branches collapse to a boolean,
+and other affected `oneOf` branches are presented as `anyOf` to retain branch
+guidance without making overlapping widened branches reject inputs.
+This can make the advertised schema accept inputs the canonical contract
+rejects. The MCP handler still validates every call with the canonical
+contract. The Gemini CLI verifier checks the outgoing
+`parametersJsonSchema` and canonical contract examples against that declaration
+using a loopback model fixture; it does not establish live Google API or
+OpenCode client behavior. Set `REA_VERIFY_GEMINI_SCHEMA_PROFILE=compact` to
+verify the compact advertisement through the same client boundary.
+
 ### Compact input schema profile
 
 Some function-calling providers reject a request while any single tool's

scripts/verify-gemini-client.mjs

@@ -5,6 +5,11 @@ import { tmpdir } from "node:os";
 import { join, resolve, sep } from "node:path";
 import { fileURLToPath } from "node:url";
 import Ajv2020 from "ajv/dist/2020.js";
+import {
+  schemaArrays,
+  schemaChildren,
+  schemaMaps,
+} from "../dist/contracts/inputSchemaPresentation.js";
 import {
   TOOL_CONTRACTS,
   toolContract,
@@ -17,6 +22,8 @@ const repo = fileURLToPath(new URL("..", import.meta.url));
 const runtimeRoot = process.env.REA_VERIFY_RUNTIME_ROOT ?? repo;
 const command = process.env.REA_VERIFY_GEMINI_COMMAND ?? "gemini";
 const mode = process.argv[2] ?? "call";
+const schemaProfile = process.env.REA_VERIFY_GEMINI_SCHEMA_PROFILE ?? "full";
+assert(["full", "compact"].includes(schemaProfile));
 // npm installs of Gemini CLI provide a JavaScript entry point; on Windows only a gemini.cmd shim reaches
 // PATH, which Node does not spawn without a shell, so a selected .js entry runs under this Node. It is
 // resolved once, because the preflight runs from the caller's directory and the client from the workspace.
@@ -60,6 +67,7 @@ const environment = {
   GEMINI_CLI_NO_RELAUNCH: "1",
   GEMINI_CLI_TRUST_WORKSPACE: "true",
   REA_PROCESS_RUN_ID: verifier.run_id,
+  REA_MCP_INPUT_SCHEMA_PROFILE: schemaProfile,
 };
 let clientVersion;
 try {
@@ -161,8 +169,43 @@ let skillRequested = false;
 let finalSeen = false;
 let catalogSize = 0;
 let schemasChecked = 0;
+let examplesChecked = 0;
 let artifactDigest;
 const schemaValidator = new Ajv2020({ strict: false, validateFormats: false });
+const booleanLiteralPath = (schema, path = "$", seen = new Set()) => {
+  if (!schema || typeof schema !== "object" || seen.has(schema))
+    return undefined;
+  seen.add(schema);
+  for (const [key, child] of Object.entries(schema)) {
+    const childPath = `${path}.${key}`;
+    if (key === "const" && typeof child === "boolean") return childPath;
+    if (
+      key === "enum" &&
+      Array.isArray(child) &&
+      child.some((item) => typeof item === "boolean")
+    )
+      return childPath;
+    const schemaChildrenAtKey =
+      schemaMaps.has(key) &&
+      child &&
+      typeof child === "object" &&
+      !Array.isArray(child)
+        ? Object.entries(child).map(([name, item]) => [
+            `${childPath}.${name}`,
+            item,
+          ])
+        : schemaArrays.has(key) && Array.isArray(child)
+          ? child.map((item, index) => [`${childPath}[${index}]`, item])
+          : schemaChildren.has(key)
+            ? [[childPath, child]]
+            : [];
+    for (const [nestedPath, nested] of schemaChildrenAtKey) {
+      const found = booleanLiteralPath(nested, nestedPath, seen);
+      if (found !== undefined) return found;
+    }
+  }
+  return undefined;
+};
 const extractEvidence = (value) => {
   if (typeof value === "string") {
     if (
@@ -226,6 +269,22 @@ const fixture = await createGeminiModelFixture({
           schemaValidator.validateSchema(tool.parametersJsonSchema),
           `${tool.name}: invalid advertised JSON Schema: ${JSON.stringify(schemaValidator.errors)}`,
         );
+        const booleanLiteral = booleanLiteralPath(tool.parametersJsonSchema);
+        assert.equal(
+          booleanLiteral,
+          undefined,
+          `${tool.name}: Gemini SDK declaration retains a boolean const/enum at ${booleanLiteral}`,
+        );
+        const name = tool.name.slice(prefix.length);
+        const contract = toolContract(name);
+        const validate = schemaValidator.compile(tool.parametersJsonSchema);
+        for (const example of contract.examples) {
+          assert(
+            validate(example.input),
+            `${tool.name}: Gemini SDK declaration rejects canonical example ${example.title}: ${JSON.stringify(schemaValidator.errors)}`,
+          );
+          examplesChecked++;
+        }
         schemasChecked++;
       }
     }
@@ -356,6 +415,9 @@ try {
     client: "Gemini CLI",
     clientVersion,
     mode,
+    schemaProfile,
+    schemasChecked,
+    examplesChecked,
     passed: failure === undefined,
     artifacts: lab,
     runtimeRoot,

src/contracts/inputSchemaPresentation.ts

@@ -146,6 +146,195 @@ const inputGroup = (branch: Readonly<Record<string, unknown>>): string => {
   return [...required, ...optional].join(" + ");
 };
 
+type SchemaNormalization = {
+  readonly schema: unknown;
+  readonly changed: boolean;
+};
+
+const isBooleanLiteralSchema = (schema: unknown): boolean =>
+  isObject(schema) &&
+  (typeof schema.const === "boolean" ||
+    (Array.isArray(schema.enum) &&
+      schema.enum.length > 0 &&
+      schema.enum.every((value) => typeof value === "boolean")));
+
+const isBooleanSchema = (schema: unknown): boolean =>
+  isObject(schema) &&
+  (schema.type === "boolean" || isBooleanLiteralSchema(schema));
+
+const preserveSharedDefault = (
+  schema: Record<string, unknown>,
+  branches: readonly unknown[],
+): void => {
+  if (schema.default !== undefined) return;
+  const defaults = branches
+    .filter(isObject)
+    .map((branch) => branch.default)
+    .filter((value) => value !== undefined);
+  if (
+    defaults.length > 0 &&
+    defaults.every((value) => isDeepStrictEqual(value, defaults[0]))
+  )
+    schema.default = defaults[0];
+};
+
+const normalizeAdvertisedSchema = (value: unknown): SchemaNormalization => {
+  if (!isObject(value)) return { schema: value, changed: false };
+
+  const node: Record<string, unknown> = { ...value };
+  let changed = false;
+  const normalizeMap = (map: Readonly<Record<string, unknown>>) =>
+    Object.fromEntries(
+      Object.entries(map).map(([name, child]) => {
+        const result = normalizeAdvertisedSchema(child);
+        changed ||= result.changed;
+        return [name, result.schema];
+      }),
+    );
+  const normalizeList = (list: readonly unknown[]) =>
+    list.map((child) => {
+      const result = normalizeAdvertisedSchema(child);
+      changed ||= result.changed;
+      return result;
+    });
+
+  for (const [key, child] of Object.entries(value)) {
+    if (schemaMaps.has(key) && isObject(child)) {
+      node[key] = normalizeMap(child);
+    } else if (
+      schemaArrays.has(key) &&
+      key !== "anyOf" &&
+      key !== "oneOf" &&
+      Array.isArray(child)
+    ) {
+      node[key] = normalizeList(child).map((result) => result.schema);
+    } else if (
+      schemaChildren.has(key) &&
+      key !== "not" &&
+      key !== "if" &&
+      key !== "then" &&
+      key !== "else"
+    ) {
+      const results = Array.isArray(child)
+        ? normalizeList(child)
+        : [normalizeAdvertisedSchema(child)];
+      const nestedChanged = results.some((result) => result.changed);
+      if (
+        key === "contains" &&
+        nestedChanged &&
+        value.maxContains !== undefined
+      ) {
+        delete node.contains;
+        delete node.minContains;
+        delete node.maxContains;
+        changed = true;
+      } else {
+        node[key] = Array.isArray(child)
+          ? results.map((result) => result.schema)
+          : results[0]?.schema;
+        changed ||= nestedChanged;
+      }
+    }
+  }
+
+  if (typeof node.const === "boolean") {
+    delete node.const;
+    if (node.type === undefined) node.type = "boolean";
+    changed = true;
+  }
+  if (
+    Array.isArray(node.enum) &&
+    node.enum.length > 0 &&
+    node.enum.every((item) => typeof item === "boolean")
+  ) {
+    delete node.enum;
+    if (node.type === undefined) node.type = "boolean";
+    changed = true;
+  }
+
+  const negated = Object.hasOwn(value, "not")
+    ? normalizeAdvertisedSchema(value.not)
+    : undefined;
+  if (negated?.changed) {
+    // Widening a predicate under `not` narrows the containing schema.
+    changed = true;
+    delete node.not;
+  } else if (negated !== undefined) {
+    node.not = negated.schema;
+  }
+
+  const conditional = Object.hasOwn(value, "if")
+    ? normalizeAdvertisedSchema(value.if)
+    : undefined;
+  const thenBranch = Object.hasOwn(value, "then")
+    ? normalizeAdvertisedSchema(value.then)
+    : undefined;
+  const elseBranch = Object.hasOwn(value, "else")
+    ? normalizeAdvertisedSchema(value.else)
+    : undefined;
+  if (conditional?.changed) {
+    // Changing the predicate can route canonical-valid inputs into a rejecting branch.
+    changed = true;
+    delete node.if;
+    delete node.then;
+    delete node.else;
+  } else {
+    if (conditional !== undefined) node.if = conditional.schema;
+    if (thenBranch !== undefined) {
+      node.then = thenBranch.schema;
+      changed ||= thenBranch.changed;
+    }
+    if (elseBranch !== undefined) {
+      node.else = elseBranch.schema;
+      changed ||= elseBranch.changed;
+    }
+  }
+
+  for (const combinator of ["anyOf", "oneOf"] as const) {
+    const branches = value[combinator];
+    if (!Array.isArray(branches)) continue;
+    const normalized = normalizeList(branches);
+    const schemas = normalized.map((result) => result.schema);
+    const branchesChanged = normalized.some((result) => result.changed);
+    if (combinator === "oneOf" && branchesChanged) {
+      const booleanLiteralsOnly = branches.every(isBooleanLiteralSchema);
+      if (booleanLiteralsOnly) {
+        node.type = "boolean";
+        preserveSharedDefault(node, schemas);
+        delete node.oneOf;
+        changed = true;
+        continue;
+      }
+      // `anyOf` retains branch guidance without allowing widened branches to
+      // reject inputs that were accepted by exactly one canonical branch.
+      delete node.oneOf;
+      if (Array.isArray(node.anyOf)) {
+        const existingAllOf = Array.isArray(node.allOf) ? node.allOf : [];
+        node.allOf = [...existingAllOf, { anyOf: schemas }];
+      } else {
+        node.anyOf = schemas;
+      }
+      changed = true;
+      continue;
+    }
+    if (
+      branchesChanged &&
+      schemas.length > 0 &&
+      schemas.every(isBooleanSchema)
+    ) {
+      node.type = "boolean";
+      preserveSharedDefault(node, schemas);
+      delete node[combinator];
+      changed = true;
+      continue;
+    }
+    node[combinator] = schemas;
+    changed ||= branchesChanged;
+  }
+
+  return { schema: node, changed };
+};
+
 // Anthropic tool input schemas reject anyOf, oneOf, and allOf at the root, and
 // clients then drop the tool or advertise it without parameters. Present a
 // root union of strict object groups as one object whose properties are the
@@ -215,7 +404,11 @@ export const presentInputJsonSchema = (
 ): Record<string, unknown> => {
   const flattened = flattenRootObjectUnion(root);
   const described = describeSchema(flattened, flattened, describeProperty);
-  if (!isObject(described)) return flattened;
+  if (!isObject(described))
+    return normalizeAdvertisedSchema(flattened).schema as Record<
+      string,
+      unknown
+    >;
   const {
     dependencies: _dependencies,
     dependentRequired: _dependentRequired,
@@ -237,12 +430,19 @@ export const presentInputJsonSchema = (
               ]
             : [],
         );
-  if (dependencyGuidance.length === 0) return presentation;
+  if (dependencyGuidance.length === 0)
+    return normalizeAdvertisedSchema(presentation).schema as Record<
+      string,
+      unknown
+    >;
   const description = [
     typeof presentation.description === "string"
       ? presentation.description
       : undefined,
     ...dependencyGuidance,
   ].filter((text) => text !== undefined);
-  return { ...presentation, description: description.join(" ") };
+  return normalizeAdvertisedSchema({
+    ...presentation,
+    description: description.join(" "),
+  }).schema as Record<string, unknown>;
 };

src/contracts/toolInputReferences.test.ts

@@ -379,3 +379,193 @@ describe("root input presentation", () => {
     });
   });
 });
+
+describe("advertised Boolean literals", () => {
+  it("keeps canonical boolean-literal inputs accepted after advertisement", () => {
+    const canonical = {
+      type: "object",
+      properties: {
+        enabled: { type: "boolean", const: false },
+      },
+      required: ["enabled"],
+      additionalProperties: false,
+    };
+    const advertised = presentInputJsonSchema(canonical, () => undefined);
+    const canonicalValidate = new Ajv2020({ strict: false }).compile(canonical);
+    const advertisedValidate = new Ajv2020({ strict: false }).compile(
+      advertised,
+    );
+
+    expect(canonicalValidate({ enabled: false })).toBe(true);
+    expect(canonicalValidate({ enabled: true })).toBe(false);
+    expect(advertisedValidate({ enabled: false })).toBe(true);
+    expect(advertisedValidate({ enabled: true })).toBe(true);
+    expect(advertised.properties).toEqual({ enabled: { type: "boolean" } });
+  });
+
+  it("drops affected negation and conditional groups without rejecting canonical inputs", () => {
+    const negated = {
+      type: "object",
+      properties: {
+        flag: { type: "boolean", not: { const: false } },
+      },
+    };
+    const negatedAdvertisement = presentInputJsonSchema(
+      negated,
+      () => undefined,
+    );
+    const canonicalNegated = new Ajv2020({ strict: false }).compile(negated);
+    const advertisedNegated = new Ajv2020({ strict: false }).compile(
+      negatedAdvertisement,
+    );
+    expect(canonicalNegated({ flag: true })).toBe(true);
+    expect(canonicalNegated({ flag: false })).toBe(false);
+    expect(advertisedNegated({ flag: true })).toBe(true);
+
+    const conditional = {
+      type: "object",
+      properties: {
+        choice: {
+          if: { const: false },
+          then: { type: "string" },
+          else: { type: "boolean" },
+        },
+      },
+    };
+    const conditionalAdvertisement = presentInputJsonSchema(
+      conditional,
+      () => undefined,
+    );
+    const canonicalConditional = new Ajv2020({ strict: false }).compile(
+      conditional,
+    );
+    const advertisedConditional = new Ajv2020({ strict: false }).compile(
+      conditionalAdvertisement,
+    );
+    expect(canonicalConditional({ choice: true })).toBe(true);
+    expect(advertisedConditional({ choice: true })).toBe(true);
+    expect(conditionalAdvertisement.properties).toEqual({
+      choice: {},
+    });
+  });
+});
+
+describe("advertised Boolean schema composition", () => {
+  it("widens an affected oneOf to anyOf when branches could overlap", () => {
+    const canonical = {
+      type: "object",
+      properties: {
+        flag: {
+          oneOf: [{ type: "boolean", const: false }, {}],
+        },
+      },
+    };
+    const advertised = presentInputJsonSchema(canonical, () => undefined);
+    const canonicalValidate = new Ajv2020({ strict: false }).compile(canonical);
+    const advertisedValidate = new Ajv2020({ strict: false }).compile(
+      advertised,
+    );
+    expect(canonicalValidate({ flag: true })).toBe(true);
+    expect(canonicalValidate({ flag: false })).toBe(false);
+    expect(advertisedValidate({ flag: true })).toBe(true);
+    expect(advertised).toHaveProperty(["properties", "flag", "anyOf"]);
+  });
+
+  it("retains nested branch guidance when widening oneOf to anyOf", () => {
+    const canonical = {
+      type: "object",
+      properties: {
+        selection: {
+          oneOf: [
+            {
+              type: "object",
+              properties: {
+                source: { type: "string" },
+                mode: { type: "boolean", const: false },
+              },
+              required: ["source", "mode"],
+              additionalProperties: false,
+            },
+            {
+              type: "object",
+              properties: {
+                target: { type: "string" },
+                mode: { type: "boolean", const: true },
+              },
+              required: ["target", "mode"],
+              additionalProperties: false,
+            },
+          ],
+        },
+      },
+    };
+    const advertised = presentInputJsonSchema(canonical, () => undefined);
+    const canonicalValidate = new Ajv2020({ strict: false }).compile(canonical);
+    const advertisedValidate = new Ajv2020({ strict: false }).compile(
+      advertised,
+    );
+    const example = { selection: { source: "capture.json", mode: false } };
+    expect(canonicalValidate(example)).toBe(true);
+    expect(advertisedValidate(example)).toBe(true);
+    expect(advertised).toMatchObject({
+      properties: {
+        selection: {
+          anyOf: [
+            { properties: { source: { type: "string" } } },
+            { properties: { target: { type: "string" } } },
+          ],
+        },
+      },
+    });
+  });
+
+  it("removes a nested not when widening a boolean item predicate", () => {
+    const canonical = {
+      type: "object",
+      properties: {
+        values: {
+          type: "array",
+          not: { items: { type: "boolean", const: false } },
+        },
+      },
+    };
+    const advertised = presentInputJsonSchema(canonical, () => undefined);
+    const canonicalValidate = new Ajv2020({ strict: false }).compile(canonical);
+    const advertisedValidate = new Ajv2020({ strict: false }).compile(
+      advertised,
+    );
+    expect(canonicalValidate({ values: [true] })).toBe(true);
+    expect(advertisedValidate({ values: [true] })).toBe(true);
+    expect(advertised).toHaveProperty(["properties", "values"], {
+      type: "array",
+    });
+  });
+
+  it("normalizes schema keywords only and preserves literal payloads", () => {
+    const literal = {
+      const: false,
+      enum: [false],
+      properties: { nested: { const: true } },
+    };
+    const presented = presentInputJsonSchema(
+      {
+        type: "object",
+        properties: {
+          default: { type: "boolean", const: false },
+          allowed: { enum: [false, true] },
+          kind: { type: "string", const: "exact" },
+        },
+        default: literal,
+        examples: [literal],
+      },
+      () => undefined,
+    );
+    expect(presented.properties).toEqual({
+      default: { type: "boolean" },
+      allowed: { type: "boolean" },
+      kind: { type: "string", const: "exact" },
+    });
+    expect(presented.default).toEqual(literal);
+    expect(presented.examples).toEqual([literal]);
+  });
+});

tests/boundary/mcp/compactInputSchemaMcp.test.ts

@@ -21,7 +21,10 @@ import { processScenarioSchema } from "../../../src/domain/process/processScenar
 import { EvidenceMcpServer } from "../../../src/server/EvidenceMcpServer.js";
 import { ToolResultDelivery } from "../../../src/server/toolResult.js";
 import { toolRegistrationOptions } from "../../../src/server/toolRegistrationOptions.js";
-import { arrayItemSchemaError } from "../../fixtures/mcpClientSchemaConstraints.js";
+import {
+  arrayItemSchemaError,
+  booleanLiteralSchemaError,
+} from "../../fixtures/mcpClientSchemaConstraints.js";
 
 interface AdvertisedTool {
   readonly name: string;
@@ -225,6 +228,9 @@ describe("MCP compact schema constraints", () => {
     );
     for (const tool of tools) {
       expect(arrayItemSchemaError(tool.inputSchema, tool.name)).toBeUndefined();
+      expect(
+        booleanLiteralSchemaError(tool.inputSchema, tool.name),
+      ).toBeUndefined();
       expect(
         ajv.validateSchema(tool.inputSchema),
         `${tool.name}: ${ajv.errorsText(ajv.errors)}`,

tests/boundary/mcp/toolSchemaValidity.test.ts

@@ -9,7 +9,10 @@ import { TOOL_CONTRACTS } from "../../../src/contracts/toolContracts.js";
 import { emptyArraySchema } from "../../../src/domain/emptyArraySchema.js";
 import { processScenarioSchema } from "../../../src/domain/process/processScenario.js";
 import { GENERATED_MCP_TOOL_CATALOG } from "../../fixtures/mcpToolCatalog.js";
-import { arrayItemSchemaError } from "../../fixtures/mcpClientSchemaConstraints.js";
+import {
+  arrayItemSchemaError,
+  booleanLiteralSchemaError,
+} from "../../fixtures/mcpClientSchemaConstraints.js";
 import { toolRegistrationOptions } from "../../../src/server/toolRegistrationOptions.js";
 
 interface ToolSchemas {
@@ -40,7 +43,15 @@ function schemaErrors(tools: readonly ToolSchemas[]): string[] {
           schema,
           `${tool.name}.${kind}`,
         );
-        return clientError === undefined ? [] : [clientError];
+        if (clientError !== undefined) return [clientError];
+        if (kind === "inputSchema") {
+          const literalError = booleanLiteralSchemaError(
+            schema,
+            `${tool.name}.${kind}`,
+          );
+          if (literalError !== undefined) return [literalError];
+        }
+        return [];
       } catch (cause: unknown) {
         return [
           `${tool.name}.${kind}: ${cause instanceof Error ? cause.message : String(cause)}`,
@@ -466,6 +477,35 @@ describe("MCP JSON Schema validity", () => {
       expect(recursiveReferences(tools)).toEqual([]);
       expectKnownAuthorityHints(tools);
       const byName = new Map(tools.map((tool) => [tool.name, tool]));
+      for (const side of ["before", "after"])
+        expect(byName.get("compare_web_captures")?.inputSchema).toHaveProperty(
+          [
+            "properties",
+            side,
+            "properties",
+            "inspection",
+            "properties",
+            "scripts",
+            "properties",
+            "items",
+            "items",
+            "properties",
+            "source",
+            "anyOf",
+          ],
+          expect.arrayContaining([
+            expect.objectContaining({
+              properties: expect.objectContaining({
+                reason: { type: "string" },
+              }),
+            }),
+            expect.objectContaining({
+              properties: expect.objectContaining({
+                artifact: expect.objectContaining({ type: "object" }),
+              }),
+            }),
+          ]),
+        );
       const catalogProjection = tools.map((tool) => ({
         name: tool.name,
         title: tool.title,
@@ -578,7 +618,11 @@ describe("MCP root input schemas", () => {
             (name === "inspect_web_page" && flag === false);
           const parsed = contract.inputSchema.safeParse(input);
           expect(parsed.success, `${name}: ${String(flag)}`).toBe(accepted);
-          expect(validate(input), `${name}: ${String(flag)}`).toBe(accepted);
+          // The advertisement relaxes Boolean literals; the canonical parser
+          // still rejects false when this operation requires script sources.
+          expect(validate(input), `${name}: ${String(flag)}`).toBe(
+            flag === undefined || typeof flag === "boolean",
+          );
           if (parsed.success && flag === undefined)
             expect(parsed.data).toMatchObject({
               include_script_sources: name === "analyze_web_bundle",
@@ -831,6 +875,21 @@ it("checks client array constraints in schema positions while preserving literal
   ).toBe(
     "broken.properties.examples: tool parameters array type must have items",
   );
+  const booleanMetadata = {
+    type: "object",
+    properties: { default: { type: "boolean", const: false } },
+    default: { const: true },
+    examples: [{ enum: [false] }],
+  };
+  expect(
+    booleanLiteralSchemaError(
+      { ...booleanMetadata, properties: {} },
+      "literal",
+    ),
+  ).toBeUndefined();
+  expect(booleanLiteralSchemaError(booleanMetadata, "literal")).toBe(
+    "literal.properties.default.const is boolean",
+  );
 });
 
 it.each([false, true])(

tests/fixtures/mcpClientSchemaConstraints.ts

@@ -36,3 +36,36 @@ export const arrayItemSchemaError = (
   }
   return undefined;
 };
+
+/** Reject Gemini-incompatible boolean literals in advertised input positions. */
+export const booleanLiteralSchemaError = (
+  schema: unknown,
+  path: string,
+): string | undefined => {
+  if (!isRecord(schema)) return undefined;
+  if (typeof schema.const === "boolean") return `${path}.const is boolean`;
+  if (
+    Array.isArray(schema.enum) &&
+    schema.enum.some((value) => typeof value === "boolean")
+  )
+    return `${path}.enum contains a boolean`;
+  for (const [key, value] of Object.entries(schema)) {
+    const children =
+      schemaMaps.has(key) && isRecord(value)
+        ? Object.entries(value).map(
+            ([name, child]) => [`${key}.${name}`, child] as const,
+          )
+        : schemaArrays.has(key) && Array.isArray(value)
+          ? value.map(
+              (child: unknown, index) => [`${key}[${index}]`, child] as const,
+            )
+          : schemaChildren.has(key)
+            ? [[key, value] as const]
+            : [];
+    for (const [suffix, child] of children) {
+      const error = booleanLiteralSchemaError(child, `${path}.${suffix}`);
+      if (error !== undefined) return error;
+    }
+  }
+  return undefined;
+};