gmail_list_labels

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

Annotations already declare readOnlyHint=true, and the description adds a useful behavioral fact: the returned values are internal ids rather than display names, and they are consumed by gmail_modify_labels. For a simple read-only listing tool with no output schema, this is meaningful context without repeating the annotations.

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?

This is two short, information-dense sentences. The first states the core result, and the second supplies the critical relationship to a sibling tool and a key gotcha about ids versus display names. No wasted words.

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 zero-parameter, read-only listing tool, the description tells an agent what it returns (labels with ids), why that matters (gmail_modify_labels needs ids), and the id-vs-display-name distinction. It could have specified the exact response envelope or array shape, but the description is adequate for correct invocation and downstream use.

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?

There are zero parameters and schema coverage is 100%, so the baseline is 4. The description appropriately focuses on return semantics instead of input semantics, since there is no input to document.

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 identifies the resource (labels) and the output (each label's id), and it distinguishes the tool from gmail_modify_labels by explaining that label ids are required there. However, it lacks an explicit verb like 'list' or 'retrieve', relying on the tool name to supply the action, which keeps it just short of a 5.

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 gives clear context: use this tool to obtain label ids needed for gmail_modify_labels, and cautions that ids are not display names. It does not explicitly state when not to use it or name alternatives, but for a zero-parameter list-all tool that guidance is largely unnecessary.

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