list_send_as

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

Annotations already declare readOnlyHint=true, so the agent knows this is a safe read operation. The description adds minimal behavioral context beyond that—it doesn't mention whether the list is ordered, filtered, or includes aliases vs. custom addresses. With annotations covering the safety profile, a 3 is appropriate because the description adds little behavioral detail.

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 a single concise sentence that front-loads the action and resource. It earns its place with no wasted words, though it could add a bit more context without becoming verbose.

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 simple read-only list tool with one optional parameter and no output schema, the description is mostly adequate. However, it doesn't clarify what 'sender addresses' includes (e.g., aliases, custom domains) or what the return format looks like, which could leave an agent uncertain about the result. The annotations cover safety, but the description could be slightly richer.

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?

Schema description coverage is 100%, so the schema already documents the accountId parameter. The description adds no additional meaning beyond what the schema provides, so the baseline 3 is correct.

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') and resource ('sender addresses available for an account'), which clearly identifies the tool's function. It doesn't explicitly distinguish it from siblings, but the resource is unique enough among the listed tools that an agent can infer its purpose.

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 implies usage context: it lists sender addresses for an account, and the schema notes the accountId is optional when exactly one account is connected. However, it doesn't explicitly state when to use this tool versus alternatives, nor does it mention any exclusions or prerequisites beyond the schema's optional account note.

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