send_message

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

With no annotations, the description carries the full burden. It states that the message will be injected into the target session and that a result is returned, which is useful. However, it omits potential side effects, failure modes (e.g., if the target session doesn't exist), or any delivery guarantees. This is adequate but not rich.

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 with a clear purpose sentence, a brief usage note, an Args section, a Returns note, and an example. Every section earns its place without excess verbosity. The front-loaded purpose sentence gives immediate clarity.

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 four parameters and an output schema, and the description covers all parameters and the return type. It includes a realistic example. While it does not address edge cases like invalid session IDs or priority handling, the given information is sufficient for an agent to select and invoke the tool correctly in most scenarios.

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 0%, but the description compensates by documenting all four parameters: target_task_id, content, source_task_id, and priority. It adds meaning beyond the schema by providing an example task ID, explaining source_task_id as the sender, and specifying allowed priority values ('normal', 'high', 'urgent'). The example call also illustrates correct parameter order.

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+resource: 'Send a message to a specific Claude Code session.' This clearly distinguishes it from siblings like broadcast_message by emphasizing targeted delivery. The additional context about communicating with another Claude instance reinforces the tool's unique role.

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 provides clear usage context: 'Use this to communicate with another Claude instance working on a related task.' It implies the targeted nature versus broadcast, and the sibling list includes broadcast_message, signaling alternatives. However, it does not explicitly state when not to use this tool or mention alternative tools by name, so it narrowly misses a 5.

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