send_message

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

Annotations already indicate readOnlyHint=false and destructiveHint=false, so the write nature is clear. The description adds the threading capability via reply_to_guid, but does not disclose additional behavioral details like permissions or rate limits.

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 extremely concise: two sentences introducing the tool, followed by a clear parameter list. No extraneous 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?

With an output schema present, the description does not need to explain return values. It covers the core functionality and parameters adequately. However, given sibling tools, additional context about when to use this over alternatives would improve completeness.

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?

Despite 0% schema description coverage, the description adds meaning to each parameter: 'chat_guid: The chat GUID to send to,' 'message: The message text,' 'reply_to_guid: Optional message GUID to reply to (creates a thread).' This goes beyond the schema names.

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 'Send a text message to an existing chat,' identifying the verb (send) and resource (text message). This distinguishes it from siblings like 'send_attachment' or 'send_message_to_address'.

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 for sending text messages to chats and mentions optional threading. However, it does not explicitly state when to use this tool versus alternatives like 'send_attachment' or 'send_message_to_address'.

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