list_allowed_recipients

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

Beyond the annotations (readOnly=true, idempotent=true, non-destructive), the description adds the edge-case behavior 'Returns an empty list when unrestricted' and spells out which operations the allowlist constrains. This is useful behavioral context that annotations alone do not convey.

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 short sentences. The first fronts the action and resource and uses an appositive to add scope; the second handles the unrestricted case. Every word adds value, with no repetition or fluff.

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 read-only, idempotent, zero-parameter list tool with an output schema present, the description covers the resource, the governing operations, and the key empty-list edge case. There is no missing information needed for an agent to select and invoke it correctly.

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 a schema_description_coverage of 100%, there is nothing semantic to add. The description correctly omits parameter details, so the baseline of 4 for a zero-parameter tool applies.

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 and resource ('List the configured recipient allowlist') and further explains what the allowlist governs by naming the send_email, forward_email, and save_to_mailbox operations. This unambiguously distinguishes it from the sibling list_allowed_senders.

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 on what the tool is for: retrieving the addresses permitted as recipients for three named operations. It does not explicitly point to list_allowed_senders as the alternative, but the recipient-focused framing makes the intended use clear enough, and the zero-parameter interface removes routing ambiguity.

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