Create Sender

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

Annotations are limited to readOnlyHint=false and destructiveHint=false, so the description carries the burden of behavioral disclosure, but 'Create a new sender identity' adds nothing. An agent learns nothing about whether duplicate nicknames are rejected, whether sender identities require verification before use, whether the operation is idempotent (idempotentHint=false), or what side effects occur. No contradiction: the write action is consistent with readOnlyHint=false.

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?

A single six-word sentence with no wasted words, front-loaded with the action verb. However, for a tool with 8 required parameters — including two nested objects — and no output schema, this brevity is arguably under-specification rather than disciplined conciseness. It earns high marks for economy but not for appropriate sizing.

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?

The tool is non-trivial: 8 required parameters, nested from/reply_to objects, no output schema, and no idempotence guarantee. The description does not explain what the tool returns on success, how failures surface, whether duplicate senders are allowed, or how the created identity relates to send_mail. There is no output schema to fill this gap, so the description is materially incomplete.

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 75%, near the threshold where the schema carries the explanatory load. The properties all have short descriptions ('ZIP code', 'City', 'Nickname for the sender'), though most are tautological. The description's 'sender identity' phrasing gently hints that the assembled fields (from, reply_to, postal address) form an identity, but it adds little meaning beyond the schema itself.

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 and resource: 'Create a new sender identity.' The purpose is unambiguous and the verb distinguishes it from the related siblings list_senders and delete_sender. However, it is very close to restating the title 'Create Sender' — the only added semantic is the word 'identity' — and it provides no detail about what constitutes a sender identity.

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 zero guidance on when to use this tool versus alternatives. With over 50 siblings including list_senders and delete_sender, and adjacent tools like create_email_list and create_contact, an agent receives no signal about the sender-identity use case or when not to call this tool. It is not misleading, but it provides no usage direction.

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