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

Goes well beyond the annotations (readOnlyHint=false, openWorldHint=true, destructiveHint=false) by disclosing the closed-chat messaging-plan requirement, the per-call confirmation default and how to disable it, that the action reaches other people, and the Cotlet API key requirement. These are concrete behavioral and auth details an agent needs before calling.

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?

Purpose is front-loaded, but the message-sending and booking-link concepts are each stated twice ('optionally with your booking link' then 'Set include_booking_link...'), creating redundancy. The safety/auth sentences earn their place but the opening could be tightened.

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 write/messaging tool with annotations covering the safety profile and a fully documented schema, the description supplies the prerequisites (existing chat, messaging plan, API key) and confirmation behavior. Nothing critical is missing, though the sibling linkage to list_conversations could be made explicit.

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 all three parameters are already documented, including include_booking_link and conversation_id. The description's mention of the booking link largely restates the schema, so it adds only marginal meaning. Baseline 3 is appropriate.

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 a client in Connect by Vagaro,' plus the optional booking-link behavior. An agent can tell this is a client-messaging action. It does not explicitly name the sibling it pairs with (list_conversations), though the schema references it.

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?

Implies usage context via 'Sends a message in an existing Connect chat' and notes the closed-chat messaging-plan prerequisite. However, it gives no explicit when-to-use vs alternatives routing; the agent must infer that conversation_id comes from list_conversations (only mentioned in the schema, not the description).

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