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

Annotations already indicate this is a mutating, non-destructive operation. The description adds useful context—the room must be approved and the mutation applies to the authenticated user's own list—but does not disclose behavior around duplicates or failure when the room is not approved.

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, tight sentence with no wasted words. The verb, target, and key constraint are all front-loaded, making it easy for an agent to parse quickly.

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?

For a simple single-parameter mutation with annotations and no output schema, the description is nearly complete. It conveys the action, the target, and the prerequisite. Idempotency or duplicate-handling details would be nice, but they aren't necessary for confident invocation.

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 description coverage is 0%, so the description must compensate for the lone room_id parameter. It adds the meaningful qualification that the room must be approved, but it doesn't explicitly map room_id to the room being saved or explain what counts as an acceptable value beyond the schema's minimum of 1.

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 uses a specific verb ('Save'), a precise resource ('an approved room'), and a clear destination ('the authenticated user’s favorites'). This immediately distinguishes it from siblings like remove_favorite and list_my_favorites.

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 clear context: this tool is for saving rooms the user wants in their favorites, and only approved rooms are eligible. It doesn't explicitly mention alternatives or exclusions, but the intended use case is evident.

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