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

Annotations already declare readOnlyHint=false and idempotentHint=false, so the write nature is known. The description adds that it 'writes a new public address,' which gives a bit more specificity about the side effect. However, it does not explain what happens to existing inboxes, whether the address is derived from the username parameter, or any limits or edge cases.

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?

Two short sentences with no filler. The action is front-loaded, and the second sentence adds a meaningful clarifying detail about the side effect. Every word earns its place.

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?

Although the tool is simple and annotations cover safety traits, the description lacks usage guidance and parameter semantics. With no output schema, the agent also cannot know what response to expect. For a create operation, this leaves notable gaps that are not compensated by annotations or schema descriptions.

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 input schema has 0% description coverage, so the description carries the full burden for parameter meaning. It does not explicitly explain 'username' or 'display_name.' The phrase 'new public address' weakly implies username is the address, but display_name is completely unexplained, leaving the agent to guess.

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 another inbox on the signed-in Cooper Email account.' It also adds the key effect, 'writes a new public address,' which distinguishes it clearly from sibling tools like cooper_list_inboxes or cooper_send_message. No confusion about what this 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 gives no guidance on when to use this tool or when to prefer an alternative. It does not mention that this is for creating additional inboxes as opposed to listing them, nor does it reference any sibling tools. Usage context must be entirely inferred from the verb 'create.'

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