Implementation of SEP-986: Specify Format for Tool Names (#900)

Co-authored-by: Felix Weinberger <fweinberger@anthropic.com>
Co-authored-by: Felix Weinberger <3823880+felixweinberger@users.noreply.github.com>
This commit is contained in:
Kent C. Dodds 2025-11-11 11:45:31 -07:00 • committed by GitHub
commit 29cb08071a
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@ -227,6 +227,10 @@ describe('ResourceTemplate', () => {
});
describe('tool()', () => {
afterEach(() => {
jest.restoreAllMocks();
});
/***
* Test: Zero-Argument Tool Registration
*/
@ -1692,6 +1696,56 @@ describe('tool()', () => {
expect(result.tools[0].name).toBe('test-without-meta');
expect(result.tools[0]._meta).toBeUndefined();
});
test('should validate tool names according to SEP specification', () => {
// Create a new server instance for this test
const testServer = new McpServer({
name: 'test server',
version: '1.0'
});
// Spy on console.warn to verify warnings are logged
const warnSpy = jest.spyOn(console, 'warn').mockImplementation();
// Test valid tool names
testServer.registerTool(
'valid-tool-name',
{
description: 'A valid tool name'
},
async () => ({ content: [{ type: 'text' as const, text: 'Success' }] })
);
// Test tool name with warnings (starts with dash)
testServer.registerTool(
'-warning-tool',
{
description: 'A tool name that generates warnings'
},
async () => ({ content: [{ type: 'text' as const, text: 'Success' }] })
);
// Test invalid tool name (contains spaces)
testServer.registerTool(
'invalid tool name',
{
description: 'An invalid tool name'
},
async () => ({ content: [{ type: 'text' as const, text: 'Success' }] })
);
// Verify that warnings were issued (both for warnings and validation failures)
expect(warnSpy).toHaveBeenCalled();
// Verify specific warning content
const warningCalls = warnSpy.mock.calls.map(call => call.join(' '));
expect(warningCalls.some(call => call.includes('Tool name starts or ends with a dash'))).toBe(true);
expect(warningCalls.some(call => call.includes('Tool name contains spaces'))).toBe(true);
expect(warningCalls.some(call => call.includes('Tool name contains invalid characters'))).toBe(true);
// Clean up spies
warnSpy.mockRestore();
});
});
describe('resource()', () => {

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@ -40,6 +40,7 @@ import { Completable, CompletableDef } from './completable.js';
import { UriTemplate, Variables } from '../shared/uriTemplate.js';
import { RequestHandlerExtra } from '../shared/protocol.js';
import { Transport } from '../shared/transport.js';
import { validateAndWarnToolName } from '../shared/toolNameValidation.js';
/**
* High-level MCP server that provides a simpler API for working with resources, tools, and prompts.
@ -664,6 +665,9 @@ export class McpServer {
_meta: Record<string, unknown> | undefined,
callback: ToolCallback<ZodRawShape | undefined>
): RegisteredTool {
// Validate tool name according to SEP specification
validateAndWarnToolName(name);
const registeredTool: RegisteredTool = {
title,
description,
@ -678,6 +682,9 @@ export class McpServer {
remove: () => registeredTool.update({ name: null }),
update: updates => {
if (typeof updates.name !== 'undefined' && updates.name !== name) {
if (typeof updates.name === 'string') {
validateAndWarnToolName(updates.name);
}
delete this._registeredTools[name];
if (updates.name) this._registeredTools[updates.name] = registeredTool;
}

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@ -0,0 +1,127 @@
import { validateToolName, validateAndWarnToolName, issueToolNameWarning } from './toolNameValidation.js';
// Spy on console.warn to capture output
let warnSpy: jest.SpyInstance;
beforeEach(() => {
warnSpy = jest.spyOn(console, 'warn').mockImplementation();
});
afterEach(() => {
jest.restoreAllMocks();
});
describe('validateToolName', () => {
describe('valid tool names', () => {
test.each`
description | toolName
${'simple alphanumeric names'} | ${'getUser'}
${'names with underscores'} | ${'get_user_profile'}
${'names with dashes'} | ${'user-profile-update'}
${'names with dots'} | ${'admin.tools.list'}
${'mixed character names'} | ${'DATA_EXPORT_v2.1'}
${'single character names'} | ${'a'}
${'128 character names'} | ${'a'.repeat(128)}
`('should accept $description', ({ toolName }) => {
const result = validateToolName(toolName);
expect(result.isValid).toBe(true);
expect(result.warnings).toHaveLength(0);
});
});
describe('invalid tool names', () => {
test.each`
description | toolName | expectedWarning
${'empty names'} | ${''} | ${'Tool name cannot be empty'}
${'names longer than 128 characters'} | ${'a'.repeat(129)} | ${'Tool name exceeds maximum length of 128 characters (current: 129)'}
${'names with spaces'} | ${'get user profile'} | ${'Tool name contains invalid characters: " "'}
${'names with commas'} | ${'get,user,profile'} | ${'Tool name contains invalid characters: ","'}
${'names with forward slashes'} | ${'user/profile/update'} | ${'Tool name contains invalid characters: "/"'}
${'names with other special chars'} | ${'user@domain.com'} | ${'Tool name contains invalid characters: "@"'}
${'names with multiple invalid chars'} | ${'user name@domain,com'} | ${'Tool name contains invalid characters: " ", "@", ","'}
${'names with unicode characters'} | ${'user-ñame'} | ${'Tool name contains invalid characters: "ñ"'}
`('should reject $description', ({ toolName, expectedWarning }) => {
const result = validateToolName(toolName);
expect(result.isValid).toBe(false);
expect(result.warnings).toContain(expectedWarning);
});
});
describe('warnings for potentially problematic patterns', () => {
test.each`
description | toolName | expectedWarning | shouldBeValid
${'names with spaces'} | ${'get user profile'} | ${'Tool name contains spaces, which may cause parsing issues'} | ${false}
${'names with commas'} | ${'get,user,profile'} | ${'Tool name contains commas, which may cause parsing issues'} | ${false}
${'names starting with dash'} | ${'-get-user'} | ${'Tool name starts or ends with a dash, which may cause parsing issues in some contexts'} | ${true}
${'names ending with dash'} | ${'get-user-'} | ${'Tool name starts or ends with a dash, which may cause parsing issues in some contexts'} | ${true}
${'names starting with dot'} | ${'.get.user'} | ${'Tool name starts or ends with a dot, which may cause parsing issues in some contexts'} | ${true}
${'names ending with dot'} | ${'get.user.'} | ${'Tool name starts or ends with a dot, which may cause parsing issues in some contexts'} | ${true}
${'names with leading and trailing dots'} | ${'.get.user.'} | ${'Tool name starts or ends with a dot, which may cause parsing issues in some contexts'} | ${true}
`('should warn about $description', ({ toolName, expectedWarning, shouldBeValid }) => {
const result = validateToolName(toolName);
expect(result.isValid).toBe(shouldBeValid);
expect(result.warnings).toContain(expectedWarning);
});
});
});
describe('issueToolNameWarning', () => {
test('should output warnings to console.warn', () => {
const warnings = ['Warning 1', 'Warning 2'];
issueToolNameWarning('test-tool', warnings);
expect(warnSpy).toHaveBeenCalledTimes(6); // Header + 2 warnings + 3 guidance lines
const calls = warnSpy.mock.calls.map(call => call.join(' '));
expect(calls[0]).toContain('Tool name validation warning for "test-tool"');
expect(calls[1]).toContain('- Warning 1');
expect(calls[2]).toContain('- Warning 2');
expect(calls[3]).toContain('Tool registration will proceed, but this may cause compatibility issues.');
expect(calls[4]).toContain('Consider updating the tool name');
expect(calls[5]).toContain('See SEP: Specify Format for Tool Names');
});
test('should handle empty warnings array', () => {
issueToolNameWarning('test-tool', []);
expect(warnSpy).toHaveBeenCalledTimes(0);
});
});
describe('validateAndWarnToolName', () => {
test.each`
description | toolName | expectedResult | shouldWarn
${'valid names with warnings'} | ${'-get-user-'} | ${true} | ${true}
${'completely valid names'} | ${'get-user-profile'} | ${true} | ${false}
${'invalid names with spaces'} | ${'get user profile'} | ${false} | ${true}
${'empty names'} | ${''} | ${false} | ${true}
${'names exceeding length limit'} | ${'a'.repeat(129)} | ${false} | ${true}
`('should handle $description', ({ toolName, expectedResult, shouldWarn }) => {
const result = validateAndWarnToolName(toolName);
expect(result).toBe(expectedResult);
if (shouldWarn) {
expect(warnSpy).toHaveBeenCalled();
} else {
expect(warnSpy).not.toHaveBeenCalled();
}
});
test('should include space warning for invalid names with spaces', () => {
validateAndWarnToolName('get user profile');
const warningCalls = warnSpy.mock.calls.map(call => call.join(' '));
expect(warningCalls.some(call => call.includes('Tool name contains spaces'))).toBe(true);
});
});
describe('edge cases and robustness', () => {
test.each`
description | toolName | shouldBeValid | expectedWarning
${'names with only dots'} | ${'...'} | ${true} | ${'Tool name starts or ends with a dot, which may cause parsing issues in some contexts'}
${'names with only dashes'} | ${'---'} | ${true} | ${'Tool name starts or ends with a dash, which may cause parsing issues in some contexts'}
${'names with only forward slashes'} | ${'///'} | ${false} | ${'Tool name contains invalid characters: "/"'}
${'names with mixed valid/invalid chars'} | ${'user@name123'} | ${false} | ${'Tool name contains invalid characters: "@"'}
`('should handle $description', ({ toolName, shouldBeValid, expectedWarning }) => {
const result = validateToolName(toolName);
expect(result.isValid).toBe(shouldBeValid);
expect(result.warnings).toContain(expectedWarning);
});
});

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@ -0,0 +1,115 @@
/**
* Tool name validation utilities according to SEP: Specify Format for Tool Names
*
* Tool names SHOULD be between 1 and 128 characters in length (inclusive).
* Tool names are case-sensitive.
* Allowed characters: uppercase and lowercase ASCII letters (A-Z, a-z), digits
* (0-9), underscore (_), dash (-), and dot (.).
* Tool names SHOULD NOT contain spaces, commas, or other special characters.
*/
/**
* Regular expression for valid tool names according to SEP-986 specification
*/
const TOOL_NAME_REGEX = /^[A-Za-z0-9._-]{1,128}$/;
/**
* Validates a tool name according to the SEP specification
* @param name - The tool name to validate
* @returns An object containing validation result and any warnings
*/
export function validateToolName(name: string): {
isValid: boolean;
warnings: string[];
} {
const warnings: string[] = [];
// Check length
if (name.length === 0) {
return {
isValid: false,
warnings: ['Tool name cannot be empty']
};
}
if (name.length > 128) {
return {
isValid: false,
warnings: [`Tool name exceeds maximum length of 128 characters (current: ${name.length})`]
};
}
// Check for specific problematic patterns (these are warnings, not validation failures)
if (name.includes(' ')) {
warnings.push('Tool name contains spaces, which may cause parsing issues');
}
if (name.includes(',')) {
warnings.push('Tool name contains commas, which may cause parsing issues');
}
// Check for potentially confusing patterns (leading/trailing dashes, dots, slashes)
if (name.startsWith('-') || name.endsWith('-')) {
warnings.push('Tool name starts or ends with a dash, which may cause parsing issues in some contexts');
}
if (name.startsWith('.') || name.endsWith('.')) {
warnings.push('Tool name starts or ends with a dot, which may cause parsing issues in some contexts');
}
// Check for invalid characters
if (!TOOL_NAME_REGEX.test(name)) {
const invalidChars = name
.split('')
.filter(char => !/[A-Za-z0-9._-]/.test(char))
.filter((char, index, arr) => arr.indexOf(char) === index); // Remove duplicates
warnings.push(
`Tool name contains invalid characters: ${invalidChars.map(c => `"${c}"`).join(', ')}`,
'Allowed characters are: A-Z, a-z, 0-9, underscore (_), dash (-), and dot (.)'
);
return {
isValid: false,
warnings
};
}
return {
isValid: true,
warnings
};
}
/**
* Issues warnings for non-conforming tool names
* @param name - The tool name that triggered the warnings
* @param warnings - Array of warning messages
*/
export function issueToolNameWarning(name: string, warnings: string[]): void {
if (warnings.length > 0) {
console.warn(`Tool name validation warning for "${name}":`);
for (const warning of warnings) {
console.warn(` - ${warning}`);
}
console.warn('Tool registration will proceed, but this may cause compatibility issues.');
console.warn('Consider updating the tool name to conform to the MCP tool naming standard.');
console.warn(
'See SEP: Specify Format for Tool Names (https://github.com/modelcontextprotocol/modelcontextprotocol/issues/986) for more details.'
);
}
}
/**
* Validates a tool name and issues warnings for non-conforming names
* @param name - The tool name to validate
* @returns true if the name is valid, false otherwise
*/
export function validateAndWarnToolName(name: string): boolean {
const result = validateToolName(name);
// Always issue warnings for any validation issues (both invalid names and warnings)
issueToolNameWarning(name, result.warnings);
return result.isValid;
}