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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false, and openWorldHint=false, so the safety profile is fully covered elsewhere. The description adds nothing beyond that—no return format, no ordering, no pagination, no note on what happens for a contact with no labels.

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?

Very short, which is appropriate, but the first sentence 'List Labels' is a verbatim restatement of the title and adds zero information, leaving effectively one substantive sentence.

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 one-parameter read tool with rich annotations and no output schema, the description is minimally sufficient. The main gap is that it does not disambiguate from the other label-listing tools in a large sibling set, which is the one thing an agent most needs 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?

Schema coverage is 100% and the single parameter contact_identifier is documented in the schema as the source id from contact create. The description contributes no additional meaning, so the baseline 3 applies.

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 ('List') and resource ('Labels') and adds the scope qualifier 'of a contact', which separates it from list_all_labels_of_a_conversation. However, it never names those sibling tools (list_labels, list_all_labels_of_a_conversation), so the agent must infer the distinction from the scope phrase alone.

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 prerequisites, and no mention of the near-identical siblings list_labels and list_all_labels_of_a_conversation. The agent gets no help choosing between three label-listing tools.

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