send_direct_message

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

With no annotations provided, the description carries the full burden of behavioral disclosure. It explains that the message opens a private chat (reusing existing), is pushed in real time, persists, and reaches offline users on next login. It also notes that it bypasses notification settings and sends no email. Missing are details about permissions, error handling, or response format, but the core behavior is well-covered.

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 well-structured: a brief one-sentence summary, followed by use-case context, behavioral details, a clear distinction from a sibling, and then parameter descriptions. Every sentence adds value, and it is appropriately sized for a two-parameter tool.

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 that the tool has only two parameters, no annotations, and an existing output schema, the description covers purpose, usage, behavioral details, parameter semantics, and distinction from siblings. It does not need to explain return values since the output schema is present. The description is sufficiently complete for an agent to select and invoke the tool 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 input schema has 0% description coverage, so the description must compensate. It explains that user_id is the 'res.users id of the recipient — from list_message_targets', adding a source for valid IDs. It describes message as 'plain text or simple HTML', providing format guidance. Both parameters are clearly explained beyond the schema types.

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 tool sends a 1-to-1 Discuss message appearing in the user's chat systray. It uses specific verbs 'send' and 'message', identifies the resource as a direct message, and distinguishes it from sibling tools like notify_user and send_channel_message by explaining the exact behavior.

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 explicitly contrasts with notify_user, stating that send_direct_message reaches the recipient regardless of notification settings and sends no email, whereas notify_user follows preferences and lands in the Inbox bell. It also provides typical use cases ("tell X", "message X", "warn X") and explains that it reuses existing private chats, giving clear guidance on when to use this tool.

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