message_send

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

Annotations indicate destructiveHint=false and openWorldHint=false, so the tool is safe and closed-world. The description adds that the message goes to an inbox and requires the recipient to call message_inbox to view it, providing useful behavioral context beyond annotations.

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 front-loaded with the core purpose, followed by usage guidelines and parameter details. It is concise (5 sentences) with no filler, though it could be slightly tighter by combining some sentences.

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 tool's complexity (sending to agents, broadcast, project) and the presence of an output schema, the description covers the main scenarios and constraints. It could mention message size limits or confirmation, but the provided context is sufficient for most decisions.

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 100% description coverage, but the description adds value by explaining the 'to' parameter options (agent_id, broadcast, project:<name>) and the condition that the sender must be a member for project targets. It also notes that subject helps triage, which is not in 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 clearly states 'Send a message to another agent's inbox,' providing a specific verb and resource. It differentiates from siblings like message_inbox by focusing on sending rather than reading. The use cases (delegating work, sharing findings) further clarify its 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?

The description explicitly states it is for 'async coordination' and gives examples of when to use it. It notes the recipient sees the message when calling message_inbox, implying the asynchronous nature. However, it does not explicitly mention when not to use it or list alternatives.

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