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

Annotations already mark the tool as non-read-only, non-idempotent, and non-destructive. The description adds the key behavioral trait that calls are fire-and-forget with no delivery confirmation, which the agent cannot infer from annotations. This is valuable context beyond the structured fields.

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 sentences, front-loaded with the purpose and ending with the important caveat. No filler words, every clause earns its place.

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?

The tool has an output schema, so return values need no description. The description covers the two behaviors, the state values, the conditional relevance of chat, and the fire-and-forget nature. Together with the 100%-covered schema, an agent has everything needed to call it 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 description coverage is 100%, and the schema already documents all three parameters, including the conditional requirement for chat. The description reinforces the semantics by explaining the two modes and the state values, but adds no new parameter-level information beyond the schema.

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 uses specific verbs 'Announce' and 'set' with clear resources: typing state to a chat, and account presence online/offline. It enumerates the exact state values and distinguishes the two operational modes. No other sibling tool covers presence, so it's unambiguously differentiated.

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 implies usage: when you need to broadcast a typing indicator or change account presence. It doesn't explicitly mention alternatives or exclusions, but no sibling tool serves this function. The fire-and-forget caveat tells the agent not to expect a confirmation, which is a usage-relevant constraint.

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