List Proton sender addresses

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

Annotations already declare the tool read-only, idempotent, and non-destructive, and the description adds valuable behavioral context: the first entry is the default, only listed addresses are accepted as from_address, the list is locally fixed, and received-email addresses are never sending choices even if they appear here.

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?

Every sentence carries meaningful information, and the most important purpose is stated first. The description is compact yet covers purpose, usage, constraints, and return behavior without redundancy.

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 parameterless read-only tool with an output schema, the description fully equips the agent: what the tool returns, the ordering, the default behavior, the acceptable input constraint, and the key caveat about received-email addresses. No necessary context is missing.

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 input schema leaves nothing to explain. The description goes further by describing the return shape (default_sender plus sender_addresses, primary first), adding meaning beyond the empty 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 states a specific action ('List the sender addresses this server may draft as') with a clear resource and scope. It also distinguishes its purpose from message/attachment tools by focusing on accepted sending addresses and defaults.

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 explicitly tells the agent when to call it: before offering a sending alias choice, and to verify whether an address belongs to the user. It also clarifies that the list is fixed and cannot be extended, which prevents futile attempts to modify it.

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