Wait for new email

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

The description discloses blocking behavior, early return upon arrival, empty results on timeout, and exclusion of pre-existing messages. These details go beyond the readOnlyHint and openWorldHint annotations and give the agent accurate expectations for a potentially long-running call.

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 tight paragraphs with no filler; the main verb and resource come first, followed by a use case and edge-case behavior. Every sentence contributes useful information.

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?

For a blocking read tool, the description, annotations, full parameter schema, and output schema together fully specify when and how to invoke it. The agent knows the purpose, wait semantics, timeout behavior, and that existing messages are excluded.

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%, with all four parameters documented with defaults and bounds, so the description does not need to repeat parameter details. It adds contextual framing around blocking and new messages, but no parameter-specific semantics beyond what the schema already provides.

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?

Description opens with a clear verb ('Block') and resource ('mail arrives in the folder... return the new messages'). It distinguishes itself from reading existing mail by emphasizing only new arrivals and gives a concrete example use case (verification code).

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?

States when to use it: 'wait for something expected, such as a verification code.' It also clarifies a boundary with 'nothing already in the folder is reported,' which tells the agent not to use this for reading existing mail. It does not explicitly name sibling alternatives, but the context is clear enough.

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