card_label_add

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

No annotations are provided, so the description carries the full burden. It reveals only that the label must already exist; it does not disclose authorization requirements, idempotency behavior when the label is already present, or the response shape for this mutation.

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 with no wasted text. It is appropriately sized for a simple two-parameter tool, though the trailing 'by label id' is slightly redundant.

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 mutation with fully documented parameters, the description covers the basic action. Without annotations or an output schema, it should say more about duplicate-label behavior and the result of the call, leaving a meaningful gap.

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%, so both cardId and labelId are already documented in the input schema. The description adds only a light emphasis that the label is identified by id, which is largely redundant with the schema.

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 ('applying') and resource ('an existing Trello label to a card'), and the phrase 'existing' distinguishes it from card_label_create_and_add. It does not explicitly name that sibling, but the core operation is clear.

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?

It gives a clear when-to-use condition ('when applying an existing Trello label ... by label id'), implying the label already exists. However, it does not state when not to use it or explicitly point to card_label_create_and_add for new labels.

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