Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds valuable behavioral context beyond that: the tool is auth-gated, and unauthenticated calls return AUTH_REQUIRED carrying a loginUrl, with a prescribed re-invocation flow. No contradiction with the annotations.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Two sentences with no wasted words: the first front-loads the core purpose and output content, the second covers the prerequisite and the auth-failure recovery path. Every clause earns its place.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

The tool is simple (one optional parameter, no output schema) and the description covers purpose, return content (loans with due dates), the auth prerequisite, and the failure mode. A bit more detail on the returned loan fields would help, but nothing needed for correct invocation is missing.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100%, giving the parameter its own baseline of 3. The description adds meaning beyond the schema by clarifying that mcp_session_id must be tied to LIBRARY authentication and explains the consequence of an invalid/missing session (AUTH_REQUIRED), which is behaviorally important for correct invocation.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description states a specific verb ('조회합니다' — retrieves), a specific resource (the authenticated user's current library loans), and a concrete output detail (with due dates). This clearly differentiates it from sibling library tools like get_my_library_seat, get_library_wait_status, and search_library_book, which concern seats, waitlists, and book search rather than loans.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description gives explicit usage context: an mcp_session_id authenticated against LIBRARY is required, and it spells out the full failure-recovery flow — when AUTH_REQUIRED with loginUrl is returned, show loginUrl to the user, guide browser login, and re-call with the issued session. It does not explicitly name alternatives, but the loan-specific purpose already distinguishes it from siblings.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.