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

Annotations already establish non-readOnly, non-idempotent, non-destructive, so the bar is lower. The description adds genuinely useful behavior beyond them: the agent gets its own email address and the API key is "shown once" — i.e. non-recoverable after this call. It stops short of stating whether mailboxes/billing are provisioned or what happens on duplicate localPart.

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?

One sentence, front-loaded with the create action and ending on the highest-value detail (key shown once). No filler or repetition of the title.

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?

Return behavior is disclosed and there is no output schema to explain. The main gap is the zero-required-parameter case: what an agent created with no arguments actually gets, which matters because all four params are optional.

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 coverage is 100%, including the localPart/domainToken pairing and the did:key alias note, so the schema already carries parameter meaning. The description adds no parameter-level context, which is the baseline-3 case.

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?

Specific verb and resource ("Creates a new agent") plus two distinguishing outcomes (own email address, API key returned once). Clearly separable from agent_get / agent_delete / apikey_create, though it never names those siblings explicitly.

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?

No guidance on when to register an agent versus creating a bare API key via apikey_create, no prerequisites stated, and no note that the call can succeed with zero parameters. The agent must infer all of this from the schemas.

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