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

No annotations exist, so the description carries the full behavioral burden. It adds useful side-effect context (a subscription-backed booking 'counts against their plan's sessions' and coaches can book regardless), but 'confirm-gated' merely restates the schema's confirm field, and nothing is said about permissions, errors, or whether the client is notified.

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?

The action is front-loaded, followed by conditional parameter guidance in a single dense but readable compound sentence. Slightly heavy punctuation, but every clause adds decision-relevant information.

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 7-parameter mutation tool with no annotations, no output schema, and 14% schema coverage, the description should do more. It covers subscription linkage and time format well but leaves the booking type, meeting link, and the shape of the confirmation/preview response unaddressed.

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 only 14% (only confirm is documented), so the description must compensate and partially does: it explains subscriptionId semantics and states times are ISO strings. However, type (IN_PERSON/ONLINE), meetingLink, and both scheduledStart/scheduledEnd formats remain undocumented beyond the raw schema.

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 session for a client'), which cleanly separates it from sibling tools like cancel_session, reschedule_session, list_sessions, and schedule_checkin. An agent knows what this tool creates without opening the schema.

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 clear conditional guidance on when to pass subscriptionId (plan-backed session) versus omit it (intro/one-off, no plan), and confirms booking is still possible without a plan. It stops short of naming an explicit alternative/redirect for related cases (e.g., reschedule_session for changes), so it is context-rich but not exhaustive.

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