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

With no annotations provided, the description carries the full burden of behavioral disclosure. It does disclose the idempotent no-op behavior, which is important, but omits other behavioral traits such as error handling (e.g., note not found) and whether the operation requires any permissions. The mutation aspect is implied by 'Add' but not elaborated.

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, front-loaded sentence that states the core purpose and the most critical behavioral nuance (no-op) without any redundant or tangential information. It is appropriately concise for a simple tool.

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 two-parameter tool with no output schema, the description covers the primary action and a key behavioral trait (idempotency). It does not explain return values or error cases, but given the simplicity and the clear idempotency note, it is reasonably complete. A 5 would require even more detail, which is not necessary here.

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 schema describes 'id' as 'Note ID' but leaves 'label' with no description, and schema coverage is only 50%. The description does not explicitly explain the parameters; it only implies that 'id' refers to the note and 'label' is the label to add, providing minimal additional meaning beyond the schema. The label's format or constraints are left entirely unspecified.

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 clearly states the action ('Add') and resource ('a label to a note'), which precisely matches the tool name and differentiates it from the sibling 'remove_label'. The parenthetical 'no-op if already present' additionally specifies the exact scope of the operation, making the purpose unambiguous.

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 implies usage context (adding labels to notes) and the no-op clarification gives a clear behavioral guideline (safe to call multiple times). However, it does not explicitly mention alternatives or when not to use this tool, so it stops short of a 5.

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