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

Annotations are all false, so the description carries the full burden. It discloses critical behaviors: the API key is shown only once and cannot be retrieved again, sandbox mode avoids real money/email, live mode starts at $0 and requires top-up, and there's a rate limit (10 per hour per address). This is far more than typical and directly informs agent decisions about storage and expectations.

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 informative and well-structured: it leads with the most critical fact (key-once), then clarifies the account nature, then details modes and limitations. While slightly long, every sentence carries weight. It is front-loaded with essential warnings and uses clear formatting (quotes around modes). No 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?

Given the tool's complexity (two modes, balance, rate limit, key handling), the description is remarkably complete. It covers the return value (API key once), mode-specific behavior, balance expectations, and rate limiting. The output schema is provided separately, so no need to detail the response. Nothing an agent needs to call it correctly is missing.

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%, so both parameters are described in the schema. The description adds significant meaning beyond that: it explains the practical difference between 'sandbox' and 'live' modes (notional balance, key prefix, behavior on email) and the default. For 'label', it doesn't add much beyond the schema, but the schema already covers it. This exceeds the baseline for full coverage.

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 the core action explicitly: 'Creates an agent account and returns its API key ONCE'. This is a specific verb ('creates') and resource ('agent account'), clearly distinguishing it from sibling tools like get_account (which reads) or create_campaign (which targets campaigns). It also adds clarity on what an account is ('a key and a balance'), removing ambiguity.

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 when to use the tool: when you need a new agent account. It explains the two modes ('sandbox' for trying with notional balance, 'live' for real use) and the rate limit. However, it does not explicitly compare to sibling tools or state 'use this instead of X', though the purpose is unambiguous. The sandbox vs live guidance is strong practical usage direction.

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