Single tool (x_login) with critical definition gaps. Input schema is present with 5 parameters (username, auth_token, ct0, twid, proxy), all typed as strings. However, the description is vague and does not explain WHEN to use this tool, WHAT it returns, or the security implications of capturing credentials. No output schema is documented. The tool description (67 chars) falls below the 10 - 1024 baseline and lacks actionable context. Parameters lack individual descriptions, LLMs cannot infer what 'ct0' or 'twid' mean. No error handling guidance. The tool is a write/sensitive operation (captures credentials) but lacks confirmation or dry-run patterns. STDIO transport caps overall score at 50; definition quality alone is 28.

• Expand tool description to 100 - 200 chars. Example: 'Authenticate with X account credentials (auth_token, ct0, twid, proxy). Captures credentials into in-memory session for write/private tools. Call this once per session before using tools that require X auth. Returns success confirmation without echoing tokens.'
• Add individual parameter descriptions: ct0 = 'X CSRF token (optional, required for some endpoints)', twid = 'X user ID / account ID (optional)', proxy = 'HTTP proxy URL for requests (optional, e.g. http://proxy.example.com:8080)'.
• Document output schema: { success: boolean, message: string, session_active: boolean }. Clarify that credentials are NOT returned to the LLM.
• Add error handling guidance: 'If auth fails, returns { success: false, error: "Invalid credentials" }. Verify auth_token and ct0 are current. Session is not updated on failure.'
• Rename tool to 'set_x_credentials' or 'authenticate_x_account' to clarify that it SETS session state, not just validates.