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

Annotations only indicate a mutating, non-read-only operation; the description adds crucial behavioral detail: titles are not unique, repeated calls with the same title create duplicates, and only the label itself is created. It does not discuss idempotency_key behavior or permissions, but those are partially covered by the schema and 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?

Three sentences, each earning its place: first states the core action and return value, second routes to alternatives, third warns about duplicates. Information is front-loaded and there is no filler.

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?

Given the simple tool shape, full parameter descriptions, and an output schema, the description covers purpose, scope, return value, duplicate behavior, and sibling integration. An agent has enough information to call it correctly and avoid common mistakes.

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 the baseline is 3. The description adds useful semantics for the `title` parameter: non-uniqueness, duplicate risk, and reuse guidance. It does not elaborate on `workspace` or `idempotency_key`, but the schema already documents those clearly.

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 and resource: 'Create a new label in the workspace and return its id.' It also distinguishes itself from sibling tools by saying 'Only creates the label' and pointing to task_add/task_edit for attaching it, making its scope 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?

It gives explicit when-to-use guidance: if the goal is to attach a label to a task, use task_add or task_edit instead. It also instructs the agent to check existing labels via get_context and reuse one, preventing unnecessary duplicate creation.

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