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

Annotations already declare readOnlyHint=false and openWorldHint=true. The description adds real behavioral context beyond them: messages go out under the user's name, confirmation is required by default but configurable, and the call reaches other people. It does not cover failure modes or rate limits, so it stops short of a 5.

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?

Efficient and front-loaded on the core action, but the second sentence restates the first almost verbatim ('starting a conversation if needed' vs 'starts a conversation if there is none yet'), wasting space that could carry additional guidance.

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 write tool with no output schema, the description covers the essentials an agent needs: who it reaches, the auth requirement (Cotlet API key with app access), and the confirmation policy. It could say more about what the call returns, but the coverage is solid.

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 both body and member_id are already documented, including the pointer to list_members/list_conversations. The description only reinforces that the message targets one member; the baseline 3 applies.

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 (Send) and resource (a direct message in Skool Chat to a member), plus the side effect of starting a conversation if none exists. This clearly distinguishes it from sibling read tools like list_conversations and get_conversation.

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?

Gives explicit situational guidance: confirm with the user before each call, and note that confirmation is on by default but can be switched off for this tool. It does not, however, compare against sibling send-like tools such as skool_comment_on_post, so alternative selection is left implicit.

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