Validation Errors

Overview

Validation errors are thrown when input parameters fail schema validation, when tool output doesn’t match the expected schema, when an HTTP method doesn’t match, or when a required prompt argument is missing.

Error Reference

InvalidInputError

Thrown when input parameters fail Zod schema validation. This is a public error — validation details are included in the response to help clients fix their requests.

Property	Type	Value
`code`	`string`	`INVALID_INPUT`
`statusCode`	`number`	`400`
`isPublic`	`boolean`	`true`
`validationErrors`	`any`	Zod validation error details

new InvalidInputError(message?: string, validationErrors?: any)

Example:

import { InvalidInputError } from '@frontmcp/sdk';

throw new InvalidInputError('Validation failed', {
  field: 'email',
  reason: 'Invalid format',
});

InvalidOutputError

Thrown when a tool’s output does not match the declared output schema. This is an internal error — schema details are not exposed to clients.

Property	Type	Value
`code`	`string`	`INVALID_OUTPUT`
`statusCode`	`number`	`500`
`isPublic`	`boolean`	`false`

new InvalidOutputError(errorId?: string)

If a custom errorId (e.g., a request ID) is provided, it is included in the public message for correlation. Otherwise, a generic message is returned. Example:

import { InvalidOutputError } from '@frontmcp/sdk';

throw new InvalidOutputError('req_abc123');
// Client sees: "Output validation failed. Please contact support with error ID: req_abc123"

InvalidMethodError

Thrown when a request uses the wrong HTTP method (e.g., GET instead of POST).

Property	Type	Value
`code`	`string`	`INVALID_METHOD`
`statusCode`	`number`	`400`
`isPublic`	`boolean`	`true`

new InvalidMethodError(method: string, expected: string)

Example:

import { InvalidMethodError } from '@frontmcp/sdk';

throw new InvalidMethodError('GET', 'POST');
// "Invalid method "GET". Expected "POST""

MissingPromptArgumentError

Thrown when a required prompt argument is not provided by the caller.

Property	Type	Value
`code`	`string`	`MISSING_PROMPT_ARGUMENT`
`statusCode`	`number`	`400`
`isPublic`	`boolean`	`true`

new MissingPromptArgumentError(argName: string)

Example:

import { MissingPromptArgumentError } from '@frontmcp/sdk';

throw new MissingPromptArgumentError('topic');
// "Missing required argument: topic"

Decorators

API

Errors

Overview

Error Reference

InvalidInputError

InvalidOutputError

InvalidMethodError

MissingPromptArgumentError

​Overview

​Error Reference

​InvalidInputError

​InvalidOutputError

​InvalidMethodError

​MissingPromptArgumentError

Overview

Error Reference

InvalidInputError

InvalidOutputError

InvalidMethodError

MissingPromptArgumentError