update_message_labels

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

Annotations only indicate destructiveHint=false. The description adds meaningful behavioral context: it does not move the message, requires labels to exist under the Labels/ namespace, and is intended for single-message operations. This goes beyond the minimal annotation.

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 concise sentences, front-loaded with purpose, followed by usage guidance and a prerequisite. No wasted words, easy to scan.

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?

The description covers purpose, usage, alternatives, and prerequisites. With no output schema and minimal annotations, it provides sufficient context for a straightforward label modification tool, though it omits potential return values or error behavior.

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 schema already documents all parameters with rich examples. The description reinforces the namespace convention but does not add significant new semantic meaning beyond the schema.

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 clearly states the tool's function: adding or removing Proton labels on a single message. It distinguishes itself from bulk_update_labels and indicates it does not move the message, making it specific to message label modification.

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?

Explicitly says to use for one message at a time, directs users to bulk_update_labels for multiple messages, and instructs to create missing labels first with create_folder. Provides clear usage context and alternatives.

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