modify_labels

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

With no annotations, the description carries the full burden of behavioral disclosure. It clearly states the core mutating behavior ('add and/or remove labels') and the target scope ('on a message'), but omits details such as the response format, behavior on invalid label IDs, error handling, and whether existing labels are preserved or merged. This is adequate for basic understanding but lacks depth.

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?

Two short sentences with no filler. The action is front-loaded, and the dependency on list_labels is stated in a separate sentence. Each sentence earns its place, making the description highly scannable.

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 mutation tool with no annotations and no output schema, the description doesn't mention what the tool returns or any side-effect/error semantics. However, the operation and the parameter source are sufficient for basic invocation, and the sibling list_labels is present to supply valid IDs. It is adequate but not fully complete.

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 description coverage is 0%, so the description must compensate. It adds meaningful semantic value by clarifying that 'add' and 'remove' take label IDs ('Use label ids from list_labels') rather than plain names, and by associating 'message' with the message_id parameter. It could be more explicit about optionality/combinations, but 'and/or' provides a useful hint.

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: 'Add and/or remove labels on a message.' It clearly differs from siblings like list_labels, search_messages, get_message, send_message, and create_draft, none of which modify labels. An agent can identify the tool's unique purpose immediately.

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 instruction 'Use label ids from list_labels' provides a clear prerequisite and points the agent to the correct sibling tool for obtaining valid IDs. It doesn't explicitly state when not to use this tool, but no sibling offers label modification, so an alternative-condition exclusion isn't necessary.

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