Send Message

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

The description goes well beyond the annotations by disclosing critical behavioral traits: it requires OAuth, it previews without confirm=true, and it reaches the real guest in production. These details are not captured by readOnlyHint, openWorldHint, or idempotentHint, and they are essential for safe invocation.

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 three sentences, front-loaded with the core purpose, and each subsequent sentence adds essential warnings. There is no fluff or redundancy, making it highly efficient.

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 complexity of a send operation with side effects, the description covers authentication restrictions, the preview mechanism, production impact, and a key naming constraint. No output schema is needed, and the description provides enough context to invoke the tool safely and 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?

The schema already provides 100% coverage for parameters, so the baseline is 3. The description adds value by clarifying the body should use the guest's real name (not template codes), which is not in the schema. It also reinforces the confirm parameter's behavior, though the schema already sees it.

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 'Post a message to a guest thread', which is a specific verb and resource. It distinguishes itself from sibling read tools like list_thread_messages and get_message. The additional notes about authentication and confirm behavior further clarify the tool's unique role.

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 provides clear context on when to use the tool, including the requirement for OAuth, the need for confirm=true to actually send, and the warning about reaching the real guest in production. It does not explicitly name alternative tools, but the sibling list makes the distinction obvious. The 'only previews and sends nothing' note is a strong usage qualifier.

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