list_allowed_senders

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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, and the description adds valuable context beyond that: it returns an empty list when unrestricted, and it explains the allowlist's practical effects on many sibling tools. This gives the agent a clear behavioral model without contradicting 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?

The description is slightly long due to the enumerated sibling tools, but that list is functional: it explains which tools are affected by the allowlist. The main purpose is front-loaded, and every clause contributes useful operational information.

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, idempotent tool with an output schema, the description is complete. It explains the return value in the unrestricted case, defines the allowlist, and maps its impact onto the relevant sibling tools. There are no significant gaps an agent would need to resolve elsewhere.

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?

With zero parameters and 100% schema coverage, the schema leaves nothing undocumented. The description appropriately does not need to explain parameters; the tool is parameterless and the action is straightforward.

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 ('List'), a precise resource ('configured inbound sender allowlist'), and differentiates from the sibling by focusing on inbound senders rather than recipients. It also clarifies the operational meaning of the allowlist, leaving no ambiguity about what the tool does.

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 clearly indicates when this tool is relevant: it controls which senders' mail is visible and eligible across the listed read and mutation tools. Though it does not explicitly say 'use this when you need to verify visibility or eligibility,' the context is strongly implied and the scope is well-defined relative to siblings like list_allowed_recipients.

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