Send Agent Contact Message

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

The description adds substantial behavior beyond the annotations: delivery is not confirmed by status=posted, only own-channel readback is; retries must be bounded and reuse the same mid and payload; denial must never be bypassed; replies/acks target messages/replies, not acks; and a posted message/reply removes the entire saved contact status. These are important mutation, retry, and side-effect details for a destructive non-idempotent tool.

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 compact and front-loads the core action before behavioral caveats. Some sentences are dense and jargon-heavy, such as the status=posted readback sentence, but there is little wasted text.

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?

For a 12-parameter mutation tool with an output schema, the description covers the important behavioral risks: partial delivery semantics, bounded retry rules, denial handling, reply/ack targeting, and the contact-status side effect. It is not fully complete because it does not clarify sibling selection against send_agent_message, but the key operational details are 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 coverage is 100%, so the schema already carries most parameter meaning. The description still adds useful semantics for retry behavior via the same mid and payload, and clarifies that replies/acks target messages/replies rather than acks, which goes beyond the schema text.

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 states a specific action and target: 'Post to an existing exact-audience Event channel.' That is more precise than a tautology, but it does not clearly distinguish this tool from the sibling send_agent_message or explain what makes the 'contact' variant different.

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?

It gives some situational constraints, such as posting only to an existing exact-audience Event channel and not bypassing denial on retries. However, it does not explicitly say when to use this instead of send_agent_message or other contact tools, so the agent must infer the selection rule.

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