petstore-api.loginUser

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

With readOnlyHint=true and idempotentHint=true, the annotations already cover safety, but the description adds no behavioral context beyond that. It does not explain that login likely issues a session token, that it may require username/password (which are absent from the schema), or that it could have side effects like rate limiting. The description is too sparse to help an agent understand the operational implications.

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?

The description is a single, concise sentence with no fluff. It is front-loaded and immediately communicates the core function, achieving maximum efficiency.

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?

Although the tool is simple and has an output schema (not shown) and annotations, the description omits crucial usage context. It does not explain that login typically requires credentials (which are missing from the schema), that it might invalidate previous sessions, or that it should be paired with logoutUser. For a state-changing authentication operation, more detail is needed.

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?

The tool has zero parameters, so the schema is trivially complete. Per the rubric, a baseline of 4 applies. The description does not mention parameters, but none are needed; it does not detract from the score.

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 'Logs user into the system' is a clear, specific verb+resource statement that unambiguously identifies the tool's function. It distinguishes itself from the sibling 'logoutUser' by stating the opposite action, providing mutual differentiation.

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 provides no guidance on when to use this tool versus alternatives. It does not mention prerequisites (e.g., needing to create a user first), the typical flow (login before other authenticated operations), or the need to pair with logoutUser. No when-to-use or when-not-to-use context is given.

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