selected_mail

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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered. The description usefully reveals that the result is derived from live Mail window state (implying it can be empty or change between calls), but it never states that explicitly or warns the agent about an empty selection.

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 parenthetical sentence that front-loads the resource and appends the one actionable detail. Nothing is wasted and no preamble delays the point.

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 an output schema present and no input parameters, the description covers everything needed to invoke the tool. The only missing piece is the practical caveat that a selection may be empty or stale when the Mail window is unfocused.

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, so the baseline is 4. The description correctly adds no parameter talk, and the clause about ids being usable with read_mail gives meaning to what the tool emits rather than what it takes.

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 names a specific resource — the messages currently selected in Mail's window — rather than a vague 'selection' concept, and clarifies the payload is ids rather than full messages. It also implicitly separates itself from read_mail by saying the ids are 'usable with read_mail', so the agent knows this is a lightweight handle-fetch, not a content read.

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?

It gives a clear usage path: call this to get selected message ids, then feed them to read_mail. There is no explicit 'when not to use' or mention of alternatives such as search_mail or get_thread, so it stops short of full routing guidance.

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