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

Annotations already declare readOnlyHint=false and destructiveHint=false, so the description doesn't need to restate that. It adds context about the label's role (attachable to tasks) but does not disclose return values, idempotency, or error conditions. Since annotations cover the safety profile, the description provides adequate but not rich behavioral context.

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 two sentences with zero waste. The primary action and purpose are front-loaded, and the alternative is placed at the end. Every sentence earns its place, making it highly efficient.

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 creation tool with full schema coverage and no output schema, the description tells the agent what the tool does, when to use it, and how to integrate it (via labelIds). It lacks return-value details, but that is often optional and not critical for a create operation. The description is complete enough for an agent to call it correctly.

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 input schema covers 100% of the parameters with descriptions (name, color, projectId), so the description adds no additional parameter meaning. Baseline 3 is appropriate given the high schema coverage.

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 'Add' and a specific resource 'a new label to a standalone project'. It further clarifies the purpose ('so it can be attached to tasks via create_standalone_task/update_standalone_task's labelIds') and explicitly distinguishes from update_standalone_label by naming it. This makes the tool's function unambiguous and clearly separable from siblings.

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 explicitly names the alternative tool (update_standalone_label) and the exact condition for using it ('rename/recolor an existing one'). It also implies the usage context (creating a new label for later attachment to tasks) by referencing the task tools. This is clear when/when-not guidance.

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