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

The description discloses meaningful side effects and behavior beyond the annotations: it sends an email, returns nothing on the first call, returns all books with handles on the second call, and explains the security property that mailbox access is the proof. This fully compensates for the sparse annotation hints.

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?

Three sentences carry exactly the needed information: first call behavior, second call behavior, and the security rationale. No filler or redundant restatement of the tool name.

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?

Even without an output schema, the description specifies exactly what each call returns and what the caller must provide. The two-step flow, return behavior, and security model are all covered, making it complete for an agent to invoke correctly.

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% and the schema already describes email and code meaning. The description adds value by explaining the temporal relationship: code is omitted on the first call, required on the second, and is a six-digit code sent to the email.

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 clearly defines a specific two-step recovery operation: first call triggers a six-digit code email, second call returns all books with handles for that account. The title 'Get back into a book when the handle is gone' adds a distinct purpose that separates it from the sibling tools like book_status or change_the_book.

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 explicit invocation guidance: call once with email alone, then again with email plus code. It does not explicitly name alternative tools or say when not to use it, but the call sequence and context are unambiguous.

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