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

Annotations already establish that this is a non-read-only, non-destructive, closed-world call, so the safety profile is covered. The description adds useful context that Cali is personalized with the user's Reulay history and that conversations are threaded, but says nothing about persistence, latency, or what state a new thread creates.

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?

Two sentences, no filler, and the core action is front-loaded before the threading hint. Every clause carries information an agent needs.

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 two-parameter conversational tool with no output schema, the definition covers the essentials and even hints that the reply carries a threadId for reuse. Minor gaps remain on message constraints and on what the response looks like on a first call with no threadId.

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 carry the load. It does explain threadId's role (taken from the previous reply, used to continue a conversation), which is the non-obvious parameter, but 'message' is only implied and the 2000-character limit from the schema is never surfaced.

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?

States a specific verb and resource ('Send a message to Cali, Reulay's mindset coach') and characterizes the recipient as a coach with access to the user's Reulay history, which tells an agent this is a conversational endpoint rather than a data-fetch. It does not explicitly contrast itself with chat-adjacent siblings like get_brain_tip or suggest_reset, so it falls short of 5.

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 second sentence gives a concrete continuation rule: reuse threadId from the previous reply to keep a conversation going. That is real usage guidance for multi-turn flow, but there is no statement of when to prefer this tool over siblings such as get_brain_tip or suggest_reset, and no exclusions.

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