Two tools with basic schemas and descriptions, but significant gaps in parameter documentation and error guidance. check_usage has no parameters (minimal schema), unlock_pdf has 4 parameters with descriptions but lacks enums, constraints, and output schema documentation. Descriptions are adequate (100-200 chars) but lack actionable error recovery guidance. No tool annotations (readOnlyHint/destructiveHint). Error handling returns text responses without structured guidance for LLM recovery.

• Add explicit output schemas to both tools. Example for unlock_pdf: {type: 'object', properties: {success: {type: 'boolean'}, output_path: {type: 'string'}, file_size_bytes: {type: 'integer'}, message: {type: 'string'}}, required: ['success', 'output_path', 'message']}.
• Add tool annotations in ListToolsRequestSchema response: check_usage with readOnlyHint: true; unlock_pdf with destructiveHint: true, idempotentHint: false (file writes are not idempotent).
• Restructure error responses as JSON objects with error_code, message, next_action, and recovery_params fields. E.g., {error_code: 'WRONG_PASSWORD', message: 'Incorrect password.', next_action: 'retry_with_correct_password', recovery_params: {hint: 'Try common passwords or contact document owner'}}.
• Add enum/constraint documentation to unlock_pdf parameters: password (optional, string, max 256 chars); output_path (optional, absolute path, must be writable); payment_signature (optional, base64-encoded x402 payload, required if free tier exhausted).
• Document unlock_pdf return fields explicitly: success (boolean), output_path (string, absolute path to unlocked PDF), file_size_bytes (integer), processing_time_ms (integer), message (string with status or error detail).