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

Annotations already declare readOnlyHint, idempotentHint, non-destructive and closed-world, so the safety profile is fully covered. The description adds real value by disclosing the shape of the returned data ('name and colour') even though there is no output schema. It omits scope (which labels — board, workspace, account) and whether the list is exhaustive.

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?

A single compact sentence with no filler, leading immediately with the resource and then the return fields. Every clause carries information an agent can use.

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?

With no parameters, rich annotations, and no output schema, the description covers the essentials and even hints at return values. The one meaningful gap is scope — an agent cannot tell whether this returns labels for the current board, the workspace, or the whole account, which matters before calling add_label.

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 tool takes zero parameters, so there is nothing for the description to disambiguate; baseline 4 applies. The empty schema with additionalProperties=false is consistent with the description's claim of a parameterless enumeration.

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?

States a specific verb (implicitly listing) and resource (labels applicable to cards), plus the fields returned. It is clearly distinguishable from add_label by the 'list' framing. It stops short of naming any sibling or scope, but an agent knows exactly what this retrieves.

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?

There is no when-to-use guidance, no mention of prerequisites, and no reference to alternatives such as add_label, which is the obvious follow-on consumer of this data. The usage is only inferable from the noun phrase 'labels you can put on cards', not stated.

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