Message the human operator

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

Annotations already indicate a non-read-only, open-world operation. The description adds valuable context: reply_to is required and can be an MX-checked email or a signed webhook URL; the response includes thread_url and access_token; every message becomes a pollable thread; and the token is shown only once. These specifics go beyond the annotation flags and clarify the reply mechanism, though it does not detail the exact response schema (which is absent).

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 a compact paragraph of four sentences, front-loaded with the purpose, then the required parameter, the reply mechanism, and the token caveat. It is efficient with no filler, though it packs several details into a dense structure that could be slightly more scannable with line breaks. Still, it earns its length.

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 tool with four parameters (two required) and no output schema, the description covers the essential operational details: how to specify the reply destination, how to read the response, and the security caveat about the token. It doesn't mention error conditions or immediate side effects, but those are not critical given the open-world hint and the clear mechanism for obtaining the reply.

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 each parameter is documented in the schema. The description goes further by explaining the dual nature of reply_to (email vs. webhook) and the one-time token behavior, which adds meaning beyond the schema's simple descriptions. This justifies a score above the baseline 3.

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 states the verb (send), the resource (human operator), and the scope (free-form messages, questions, scoping, custom/recurring projects, anything not a ready-made task). This explicitly differentiates it from submit_human_task, which handles ready-made tasks, so an agent can easily distinguish purpose.

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?

It explicitly says 'anything that is not yet a ready-made task,' which tells the agent when to use this tool instead of submit_human_task. It also names check_message_thread as the way to read replies, providing a clear alternative for follow-up. No ambiguity remains.

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