Send a direct message to another session

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

No annotations are provided, so the description carries the full burden of behavioral disclosure. It discloses the key delivery model: 'The recipient sees it on their next bus_receive,' which tells the agent that sending is asynchronous and queue-based. However, it does not mention failure behavior, durability guarantees, whether the recipient must exist, or what the tool returns, leaving gaps in behavioral transparency.

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 two concise sentences. It front-loads the primary action, then the key behavioral consequence, then the intended use case. Every sentence contributes unique value with no redundancy or filler.

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 description covers the core purpose, the delivery behavior, and the intended usage context. With no annotations and no output schema, it could briefly mention the return value or error cases, but for a simple send tool with fully documented parameters, the essential information needed to invoke it correctly is present.

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%, so the baseline is 3. The description adds no parameter-specific information beyond what the schema already provides; the schema accurately describes each parameter (to, from, text, subject). The description's references to 'specific session inbox' and 'handoffs' are contextual but do not add meaning to individual parameters.

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 opens with a specific verb and resource: 'Send a message to a specific session inbox.' It clearly distinguishes from siblings by emphasizing 'specific session' (as opposed to broadcast) and explicitly identifies the use case as 'handoffs and requests between agent sessions,' making its role unambiguous.

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 gives clear context for when to use the tool: 'Use for handoffs and requests between agent sessions.' It doesn't explicitly name alternative tools like bus_broadcast, but the targeted-session phrasing implies when this tool is appropriate instead of broadcasting. No exclusions or when-not-to-use guidance is provided.

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