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

Goes well beyond the annotations: it discloses refusal behavior with free windows listed, that nothing is sent to the client, the event naming convention, ownership by the caller, and the two-step propose/confirm protocol with action_id and plan_token. The only gap is that it doesn't say what happens to the proposal if it is never confirmed or how long a plan_token stays valid.

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?

Front-loads the action and the time-format constraint, then the prerequisite, then the confirmation protocol. Dense but every sentence carries operational information; the example phrase and the CONFIRMATION label aid scanning without much waste.

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?

With no output schema, the description still explains the return shape (status='confirmation_required', action_id, plan_token) and the failure mode, which is what an agent needs to drive the two-step flow. Minor incompleteness on duration_minutes and note semantics.

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 only 14%, so the description must compensate, and it does for the critical fields: start_at is local time in the company's zone, lead_id is for CRM leads, phone is optional contact info, and service feeds the event title. It leaves duration_minutes and note unexplained, which keeps it short of a 5.

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 ('Book a client appointment in the caller's company calendar') and anchors it with a concrete example utterance. It is clearly distinguishable from planner_free_slots, which it explicitly routes to for availability checks.

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 preconditions ('Check planner_free_slots for that day first'), states what happens on conflict or out-of-hours attempts, and tells the agent when to pass lead_id and phone. The confirmation flow is spelled out as the required path rather than an option.

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