list_allowed_senders

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

Annotations already declare readOnlyHint=true and idempotentHint=true, and the description adds meaningful behavioral context beyond that: it explains that when configured, only allowlisted senders' mail is visible/eligible for other tools, and that an empty list means unrestricted. This helps the agent understand the operational semantics without overstepping.

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 two sentences, front-loaded with the core action, and every sentence adds value—covering what the tool does, why it matters, and the special empty-list behavior. There is no redundant or filler content.

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 list tool with an output schema, the description is complete: it states the return type behavior (empty list when unrestricted), the relationship to other tools, and the scope (inbound sender allowlist). Nothing essential 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?

The tool has zero parameters, so there are no parameter semantics to clarify. The description correctly implies that the tool takes no input and simply returns the current allowlist, which aligns with the schema. A baseline of 4 is appropriate given the absence of parameters.

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 uses a specific verb ('List') and a specific resource ('configured inbound sender allowlist'), and clearly differentiates from the sibling tool 'list_allowed_recipients' by focusing on senders. It also explains the functional effect of the allowlist, making the purpose unmistakable.

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 states clear context: it lists the inbound sender allowlist, explains that it affects which emails are visible/eligible for read and mutation tools, and notes the empty-list behavior when unrestricted. It does not explicitly name an alternative tool, but the context is sufficient for a simple inspection tool.

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