send_message

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

With no annotations, the description carries full responsibility for behavioral disclosure. It exposes the delivery_status semantics (delivered/held/blocked), warns that held/blocked means non-delivery, and explains the 422 rejection for 'contact_card'. This is thorough, honest, and non-obvious behavior that an agent needs to know.

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?

Three dense sentences, no filler. The purpose is front-loaded, followed by critical delivery-status guidance and the content_type constraint. Every sentence carries operational value.

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 simple three-parameter send tool with no output schema, the description covers the key edge cases: checking delivery_status, the contact_card_request flow, and the forbidden contact_card value with its 422 error. No critical operational gap remains.

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%, so the description must compensate. It adds important meaning to content_type by explaining the 'contact_card_request' scenario and explicitly forbidding 'contact_card'. session_id is contextualized by 'already-open session', and message is self-explanatory. Slightly more detail on message formatting or delivery_status output shape would push it higher.

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 a specific action ('Send a message') and a specific resource/'already-open session', which immediately distinguishes it from sibling tools like open_conversation and read_conversation. The purpose is unambiguous and actionable.

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 context for when to use the tool: it must target an already-open session. It also gives explicit guidance on checking delivery_status and when to use content_type='contact_card_request', plus a hard constraint against sending 'contact_card'. It does not explicitly name alternatives, so it stops short of a 5.

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